Briggs & Stratton 18HP engine problem

krazifanJune 4, 2006

Got a strange problem here that normal maintenance isn't helping to clear up.

I've run the tractor a half dozen times this season already and all of a sudden, it will lose power after about 15 minutes of mowing. It will act like it's going to stall and then rev back up. A few seconds later it will do the same thing and rev back up. Eventually, it does stall. It does this even when I've stopped mowing and just sit there listening to it.

To try and correct I've done a maintenance including:

- change oil & filter

- change fuel filter

- replace fuel line

- replace air filter & pre-screen

- replace spark plug

- drain gas and try fresh gas

I've also taken apart the carburetor to look for clogs or deposits and it seems fine (although I didn't have the right tool to actually clean the injector.)

What I have noticed is that when it is running OK, you can see some gas collecting at the bottom of the fuel filter. When it starts to lose power, there is almost no gas at the bottom of the fuel filter. This is leading me to believe that the engine is stalling because of a fuel problem, but I'm not sure what else to check/replace. And I'm befuddled as to why it takes 15 minutes of mowing to cause the problem.

Any ideas?

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canguy(British Columbia)

Sounds like a fuel pump problem but first check that all the line fittings from the tank are tightly clamped. A loose hose will allow air into the system. Also check the impulse hose between the crankcase and pump for deterioration.

    Bookmark   June 4, 2006 at 3:37PM
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Post your engine's model numbers so we know what you have.


    Bookmark   June 4, 2006 at 3:38PM
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It's a Briggs & Stratton model 31P777, type 0299-E1

Not sure where the fuel pump is. I don't see it anywhere on the schematic or parts list.

    Bookmark   June 4, 2006 at 3:44PM
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If the fuel tank is above the engine, a fuel pump is not needed. The clear fuel filters cause a lot of problems,
as many who watch the fuel travel, or seemingly lack of
travel, through them, automatically assume the problem is
fuel related.
In your case, I would advise ignoring the fuel filter,
but instead, cheack the valve clearances, as that is
quite possibly the problem.

    Bookmark   June 4, 2006 at 4:06PM
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Run it with the gas fill cap off (fuel tank cap) and see if that helps. The gas cap may be plugged and causing gas startvation.

    Bookmark   June 4, 2006 at 4:17PM
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mowerdan(10a Clovis, CA)

I had a simular problem with my 22HP B/S engine. Cause was a pluged fuel cap causing a vacuum in the gas tank and no fuel flow. My cap has a very small vent hole about a 1/64",and was pluged, purged it with compressed air and problem solved. HTH


    Bookmark   June 4, 2006 at 7:43PM
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kismar(z5 Pa)

I agree with the above to check the fuel cap and hoses. I am unsure if it has done this all this season or just this last mow so, Second have you cleaned under the tin? Could be getting hot from a rodent condo built over the winter and cutting out.

    Bookmark   June 4, 2006 at 8:04PM
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Did you find the problem? Yet?

    Bookmark   June 5, 2006 at 4:38PM
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It is not the fuel cap. Had the same problem running without the fuel cap.

It's got something to do with an issue that builds over time. Would my symptoms be consistent with the engine overheating? If so, what can I do about that?

    Bookmark   June 5, 2006 at 6:00PM
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cgalny(z6 NY)

I agree with fisher40037: check the valves. A 15hp B&S Vanguard I had for a number of years exhibited similar problems and it was a cracked (actually broken) valve rocker.

    Bookmark   June 5, 2006 at 6:54PM
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The coil can malfunction when it gets hot too. Check the spark when the engine is cold then hot.

    Bookmark   June 5, 2006 at 7:54PM
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Well, I'm not sure how to check the valve myself. Might need to actually give in and take it to a repair shop :(

However, when I took the blower housing off and blew the engine off with a leaf blower, a decent amount of dirt/grime came off. I was able to mow (my now jungle like lawn) on the lowest speed doing half passes for an hour until the gas ran out. After I filled up the tank, I tried it at the next highest speed and it stalled out after 10 minutes :(

    Bookmark   June 5, 2006 at 8:52PM
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Since you live in the United States, you live fairly
close to me, so bring it by, and I will show you how to
check the valves, for free.

It is not hard to do, or I would have not suggested it.
Since you have the wrenches to take off the blower housing,
you can remove the valve covers too. You will need to go
to Walmart and but a set of feeler gauges for about $7.


    Bookmark   June 5, 2006 at 9:08PM
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I agree with two of the posts:

Check the valves for appropriate clearances, and then go to the ignition coil. Magnetrons are usually pretty stout, but an intermittent condition when hot is not unheard of.

    Bookmark   June 5, 2006 at 9:09PM
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Wonder what it was?

    Bookmark   June 7, 2006 at 11:50PM
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OK, so I checked the valve clearance (I think.) Went by the Briggs&Stratton site and they showed how to remove the cover, position the piston for measuring (1/4 down from top) and then measure. I opened up the intake clearance by a hair but it was really pretty close before (.002 instead of .003-.005) Is it correct that one or the other valves should be touching the bar when the piston is in different positons?

I've pulled off the carb again and I want to make sure the nozzel (injector?) is not clogged. How do I go about doing that? Or just cleaning the whole carb in general?

This tractor is only 2 seasons old (got it midway through 2004) so I'm really getting frustrated with it.

    Bookmark   June 9, 2006 at 11:28PM
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kubotamota(6A Kentucky)


    Bookmark   June 9, 2006 at 11:37PM
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When checking the clearances, rotate the flywheel and
watch the rocker arms, when the piston comes to the top,
and one rocker arm is closing and the other about to open,
then you need to rotate the flywheel one more revolution
to check the clearances. And a valve that was set at
.002, would not close fully when the engine gets hot.

On the other side of the coin, if the clearances are
too great, then the engine would be difficult to start,
as the compression release would not work.

Put your carb back on and mow.


    Bookmark   June 10, 2006 at 6:22AM
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I don't know if the problem was somewhat better or if I was just lucky. I was able to mow about 30-40 minutes before it went out this time. The engine runs fine on idle for over an hour (that's when I shut it down) but as soon as it's under load, it starts acting up.

Any possibility it has something to do with the muffler? I borrowed a neighbors tractor which has almost the same engine as mine (17hp instead of 18hp) and it sounds much smoother/quiter.

I'll double check the valve clearances again while I wait for any more help from you guys. And BTW, thanks for all the effort. I may not have fixed the problem, but I know a lot more about my engine than I did when I started :)

    Bookmark   June 11, 2006 at 3:46PM
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adjust the valves correctly, and this will be over.

    Bookmark   June 11, 2006 at 7:30PM
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You really shouldn't have to do anything on a tractor that is that new. Is it at all possible that you put 2-stroke mixed gas in your mower? I've done it back in my teen years, and it had a similar effect. The valves got covered in carbon. and when the carbon got hot the fuel would ignite as soon as it entered the cylinder.

    Bookmark   September 17, 2006 at 10:23AM
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wise_guy(NW MN)

Definately agree with Fish!

This has got to be a valve problem. It's just not getting the proper air flow to promote currect fuel draw and volumetric efficiency.

If sounds like the valves are sealing for the first 15 minutes. The gap is probably too close -- causing longer duration and carb spit-back -- but the engine is still capable of running.

As the engine heats up, the exhaust valve (the hottest part of the engine), intake valve, and pushrods will grow in length due to heat. An engine in this situation would soon be running with partially open valves and very low compression.

    Bookmark   September 23, 2006 at 1:12AM
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Is there a difference in length of the valve pushrods? There is some kind of difference because they each have different part numbers and the intake valve cost twice that of the exhaust valve.

    Bookmark   October 17, 2006 at 10:22PM
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A intake valve usually covers a larger opening because it is up to the air pressure to push air into the cylinder. an exhaust has the piston to push the exhaust out.
Also, the exhaust valve is made to handle higher temps. In cars, exhaust valves can be filled with fluids like liquid sodium to handle the heat.

maybe if larger=more material=more $$$

    Bookmark   October 18, 2006 at 12:49AM
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The exhaust pushrod is sometimes made heavier.


    Bookmark   October 18, 2006 at 9:22AM
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I have a 18.5 Briggs and the 20A fuse keeps blowing can anyone help.

    Bookmark   October 21, 2006 at 8:38PM
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WHICH 18.5 hp B&S, Model number, and what 20 amp fuse?

Walt Conner

    Bookmark   October 22, 2006 at 11:25AM
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my B&S is a Model 31P777 and is a craftman 4000 Riding mower the 20A fuse is under the dash and it the only fuse i have found

    Bookmark   October 22, 2006 at 12:13PM
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I don't think your engine has anything to do with the blowing fuses. I would look for a short in wiring harness of mower.

Walta Conner

    Bookmark   October 22, 2006 at 5:22PM
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jerryo(z4 in SE MN)

Bill(billdoug) said that "I have a 18.5 Briggs and the 20A fuse keeps blowing can anyone help."

I once had a briggs blow fuses because the charge diode was shorted. I unplugged the wire for a while, but then replaced the diode, probably with a radioshack 3 or 5 amp diode.

The diode is the fat spot on the engine side of the connector for the DC charge.

This assumes that your mower doesn't have an electric clutch.


    Bookmark   October 22, 2006 at 7:38PM
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hello .. I am also having a problem with a Briggs and Stratton 18 hp with the following info 422707 121401 9411185B Mongomery Ward tractor 1994? After all these years more and more under load, the engine would slow down reving until I took the load off. ( disengage the mower) and she would be ok. She is now at the point that now she will not start. She seems to have spark (blue) govenor seems to be working intake log for carb is wet with gas. starting fluid does no good. Would anyone have an idea? thank you

    Bookmark   October 30, 2006 at 8:08AM
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Hello Krazifan. What was the problem? I have the same exact problem with my 18HP Briggs engine. I replaced the coil and still have the same problem. Runs good for 15-20 minutes the revs up and down then quits! My email is thanks.

    Bookmark   May 17, 2007 at 6:57PM
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I have the B&S 422707 also,maybe someone can help me.The trouble I am having is no spark.I would like to know if this is right way.Battery to solenoid to stater.Now my problem the ignition,where does the positive and negative go to start the darn thing?
Thanks for some help.

    Bookmark   July 8, 2007 at 8:26AM
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You know it's too bad that we don't (somehow) require folks to come back and post the fix/results when help is asked. It would make the site much more useful as a reference.

It seems as though the general consensus for the OP was that it was his valves, but it sure would be nice to confirm!


    Bookmark   July 8, 2007 at 8:44AM
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Yes to your battery, solenoid, starter, question.

Positive feed from the ignition switch, when switch is in Start position, to little post on the Starter Solenoid.

When switch is in Off position, there needs to be continuity from a switch wire to ground. This wire attaches to the Kill Wire Terminal which is just below the cooling shroud and above where the left hand Intake Manifold attaches to block. (Facing the Carb. side of the engine)

Walt Conner

    Bookmark   July 8, 2007 at 5:03PM
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deerslayer(Z5 NE IL KBG)

I suspect that the OP adjusted his valves and solved his problem. We won't hear from him until he has his next question.


    Bookmark   July 8, 2007 at 8:00PM
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I have exact same problem as krazifan had, and the same engine model. I adjusted the valve clearance and that doesn't solve the problem. What else can I try?

The engine continues running if I throttle when it runs tough.

    Bookmark   August 28, 2007 at 1:03AM
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I also have the same problem as krazifan. The engines runs for about 15 minutes then dies, let it sit fora few minutes then it will run again then die and the cycles repeats. I can spray ether into the intake and it will fire until the ether burns out. Going to replace the solenoid at the bottom of the carb with a plug to see if it was deactivating and stopping the fuel flow.

    Bookmark   September 4, 2007 at 11:00PM
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Have either of you tried the things posted above, such as new fuel filter, clogged vent etc.?

    Bookmark   September 5, 2007 at 5:27PM
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22 HP B&S 40H777 Exact same problem...
15 minutes of load, engine starts to surge and will die. If I remove the load (blades) and pull the choke cable will keep it running a bit longer, but finally dies because of gas starvation.
Symptoms resemble vapor lock.

Cleaned fuel lines
Insulated fuel lines from heat sources
Changed fuel filter
New fuel pump
Impulse tube changed
Fuel tank cap vent cleaned
Oil filler cap tight and seals OK
Electric fuel shutoff 'appears' to work OK.

Engine restarts OK after a few minutes... indicating that it is NOT a valve adjustment problem, as everything is really HOT at this point.
Dirty carb would prevent first 15 minutes of excellent performance.
Going to open the carb tomorrow... I'll keep you posted

famous ron

    Bookmark   September 10, 2007 at 10:16PM
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Check for spark when problem occurs.

    Bookmark   September 11, 2007 at 12:50PM
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I don't how how old or how many hours these engines have on them, but it I had good spark, it's getting fuel, Valves adjusted within limits, good plugs and wires, and it runs for a while. My only other thought or guess would be Head gasket or carbon build up in the combustion chamber or chambers. IMO with carbon build up the carbon starts glowing and buring the gas before it compressed. This IMO might explain the loss of power and any kick back smoke. I would also make sure the fuel feed system is good especially the vacuum fuel pump and feed hoses to the pump. If any of these are the old Flat opposed model briggs engines I would suspect carbon build up or cooling fins plugged. Food For thought???????????

    Bookmark   September 11, 2007 at 9:51PM
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I removed the carb solenoid and just put a plug in it. It ran and never shut down. I know what the solenoid does now but I'm not sure if I really need it.

    Bookmark   September 11, 2007 at 10:16PM
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Does the engine backfire right after you shut it down? The solenoid is there to stop that. If it doesnt happen, you might not need it after all.

If it *does* happen, a suggested remedy is to lower the engine speed to idle for 15-30 seconds and THEN shut it down. The fuel being pulled into the engine shouldnt make it to the muffler as unburnt fuel and it wont backfire anymore.

If it were me and the solenoid was causing a problem, and it was there from day 1 (factory installed), Id eventually get a new solenoid (unfortunately brand new they are NOT cheap!!)


    Bookmark   September 12, 2007 at 8:31AM
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Chris, yeah, they're about $60 something....I just bought this mower used and it backfired when I throttled down when I got it. If I ease the throttle back, the backfiring is might need a tuneup, valves adjusted....but I'm pretty sure now the solenoid was causing it to die. Question on the valve adjust..if I pull the valve cover do I need to drain the oil or will it not leak out all over the place?

    Bookmark   September 12, 2007 at 7:52PM
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I had a similar problem (to the original poster way up at the top of this thread) with a Sears garden tractor that I recently inherited and brought back to working condition. It would run for some time, then die, fuel starved.

Just for giggles, I hooked my vacuum gauge into the fuel line upstream of the filter, and found that during the failure the vacuum in the line was about 3mm/Hg. Something was blocking the fuel line. I found that the outlet nipple of the plastic gas tank had been crushed (by an over-torqued worm drive hose clamp) at some point in the past and was collapsing.

I fashioned a stent of sorts by cutting the ring off of a 12AWG crimp-on ring lug and inserted the remaining barrel into the outlet nipple of the tank, where it would prevent the nipple from collapsing. Problem solved.

    Bookmark   September 16, 2007 at 12:57AM
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In the post above, "3mm/Hg" should be "3in/Hg". 3 millimeters of mercury ain't much!

    Bookmark   September 16, 2007 at 1:53PM
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18 hp briggs 422707, recently rebuilt the carb,and adjust the gov. to around 3000rpm. my problem is it seems to misfire all the time. my plugs are sparking and after inspecting them they look to be at normal operating temp(not running rich, or lean) whats is causing this. is there timing,(it doesnt look like there is). i thought i read that there is no fuel adjustment on the carb, is that true. what would you recommend.

in regards to the issues of 15 mins running then dieing. is it possible the gas tank cap isnt allowing air to pass and creating vacuum in the tank.

    Bookmark   September 18, 2007 at 1:48AM
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Finally got into the carburetor and did some simple cleaning... I really think it was the shut off valve on the bottom of the float bowl. Blew it clean with a air nozzle.... then put 12 volts to it (to open the valve) and blew it clean again. Everything appeared to be very clean... no water, no grit after 400 hours of heavy use.

I did CHECK the valve clearance...but did NOT adjust them. Specs call for .004-.006 for both intake and exhaust. Actual settings are .012-.013.. (too loose) but it runs GREAT. These were very precise measurements, repeated many times.
If it looks like a gas problem, sounds like a gas problem, and acts like a gas problem... stay away from the valves.
Good hunting...

Famousron (I'm famous 'cause I make GREAT jerky)

    Bookmark   September 19, 2007 at 10:51PM
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Nicklow241: If the engine has more than a few hundred hours on it, you might try pulling the heads and wire-brushing to remove the carbon deposits that have certainly built up on the combustion chamber and piston. If the miss worsens as the engine temperature increases, it's almost certainly carbon in the combustion chamber causing preignition.

Depending upon the type number and manufacture date of the engine, it may or may not have a high speed mixture adjustment. If the type number (of the engine) is 1100 or above and the date code is 98101500 or above, there's no high speed adjustment. Type numbers 1100 and above built before 98101500 may or may not have a high speed adjustment, while type numbers below 1100 always have them. If there's only one needle valve visible on the carb exterior, it's always idle mixture -- if there are two, then you have an adjustable high speed circuit. The idle mixture adjustment only has effect when the throttle is fully closed, of course.

There is no timing adjustment at all -- if the flywheel key isn't partially or fully shorn, then your ignition timing is right where it belongs and needn't be messed with.

    Bookmark   September 22, 2007 at 5:40PM
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I am having the same problem and tried the easy fixes which didn't work. Please post any successful fixes you may have. Thanks

    Bookmark   October 2, 2007 at 5:23PM
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Hi all, First let me say that I think what you are doing here is great, as the general public needs a place to get great answers from. I have a Duetz-Allis 816 tractor. The problem I am having is that the lower butterfly assembly only opens about to 3/4 throttle, then stops. I can not find any adjustments for this. Unfortunately this is too low of a speed to engage the mower deck, or to even drive it accross the lawn. Any suggestions as to what I should be looking for? The governor spring is totally relaxed at this position.

    Bookmark   April 9, 2008 at 3:16PM
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Briggs Vanguard V twin 18hp model 350447 Type 0064-01 1880

I've had a similar problem to other owners "engine sounds like it's running out of fuel after 15-30 minutes use and keeps running if it's choked". I adjusted the valves and it starts easier, I guess the valves were too loose to allow the decompressor to operate but it still stalls out. I haven't tried the fuel solenoid yet but I can here it click when I turn the key on and off so it is doing something.
A theory I was thinking about today; is there any chance that because the ethanol content is going up in fuel the boiling point is going down? These air cooled motors run awful hot and the downdraft carb sits in a pretty warm location. This web site says the boiling point for gasoline is between 100-400F which is a pretty wide range. Any comments?

    Bookmark   July 7, 2008 at 10:00PM
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I had the same problem with my scag tiger cub; mower would stall and quit after 15 minutes to an hour. I tried everything (drained and cleaned the fuel tanks, replaced fuel pump, replaced fuel lines, replaced fuel filter and cleaned the carb.) I was finally fed up and going to buy a new carb when I got a second opinion from a guy who used to work on mowers. The first thing he did was take off the carb and look at it closely. One of the 2 jets looked closed so he unscrewed it and blew into it and a piece of trash that was fitting perfectly in the jet came out. The trash looked like a piece of the paper element from the fuel filter. Replaceing the carb would have fixed my problem but thankfully he saved me some money. It has been months and the mower works great.

    Bookmark   July 8, 2008 at 4:36PM
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i wonder if you actually cleaned out the cylinders well enough - i recently cleaned up a mower - and there was no possible way a leaf blower would have removed the crap from the cylinders I was working on...

If your not sure - go back and gunk down those cylinders real good - and ensure you got them all unplugged.

The motor i finished cleaning up looks like new - and runs "almost" like new... I can clearly see a difference in that motors performance.

Secondly - thats a lot of valve lash you stated - at one point you can have too much lash and then drop a push rod -- or even worse - potentially send a valve through a piston...

id have that taken care of sooner than later.

good luck

    Bookmark   July 8, 2008 at 5:16PM
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I had exactly the same problem with a John Deere L108 would run for 15 mins then die - could idle back to the garage if you were lucky. Tried replacing the coil and read all the posts about valve clearances but didn't want to go there... Fuel pump seemed to be working fine. Took the carb apart and cleaned but didn't find anything obvious. THEN I tried the carb solenoid. Took it out and saw that it operated when the key was turned on. Tried heating it with a little gas torch but it stayed pulled in. Found a plastic plug to fit the bottom of the carb and stuck that in there - NOW MOWER GOES GREAT. Will probably look at getting a replacement solenod but goes fine without it - I think it is there to cut off gas when you turn it of to prevent back firing... (Got the solenoid thru Sears parts...)

    Bookmark   September 14, 2008 at 10:10AM
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I am having problems with my Briggs & Stratton 18.5 hp lawn tractor similar to those described above - runs rough then stops running when hot. I've rebuild the carb and replaced the coil. It runs better at first, but still stalls and won't restart after it gets hot. I want to try removing the carb solenoid to give that a try. Can anyone tell me where the solenoid is on this motor? I assume on the carb, but I don't see it! Thanks.

    Bookmark   September 21, 2008 at 10:00PM
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jkorn1317, PLEASE start a NEW thread outlining your problem and post the engine numbers from the engine (on shroud or valve cover) Model #, Type #, and Code #, please. Without these numbers nobody can even begin to look for the Illustrated Parts List for your engine to see if it has a fuel solenoid (or not). If you don't see something with a wire leading from it, attached (threaded in actually) to the carb float bowl, it probably does not feature a fuel cutoff solenoid. Though I doubt it would be a defective solenoid (because it does run some). A defective or stuck fuel solenoid usually results it not running at all.

    Bookmark   September 22, 2008 at 8:03PM
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I had the same issues with mower dying after about 15 minutes of cutting. Turned out to be the fuel solenoid if you take it off the bottom of the carb you will note on the top of the plunger their is a plastic cap designed to plug the main jet on shut off. This cap has worked its way up the knurled shaft and shuts off the fuel flow. A good friend and master mechanic was able to diagnose and repair the old one using epoxy and pushing it all of the way down on the shaft.

    Bookmark   October 2, 2008 at 5:27PM
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I had a similar problem to many here a few months ago with my 3-year old craftsman lawn tractor, stalling out, black smoke, tough to start after a certain period of time. Mine was Sears lawn tractor 917.275371, Engine Briggs & Stratton 31C707. After finding Sears charged $95 for diagnosis and estimate only, and the only local repair guy was backed up 3 weeks, wife got book for me from library. I fixed mine, tracked it down to the choke stuck in closed position. Apparently the shaft on these is engineered a little too large, and dirt gets in there so that it doesn't open on its own; pushing the throttle all the way up closes it to get the engine started, but this often sticks and doesn't return to the open position when you set the throttle to "mow". So you need to modify this. See picture at See the black lever that's on top of the choke shaft, center of photo? I drilled a small hole in the plastic housing and inserted a small spring in the hole, and the other end in the already-existing hole in that black choke lever (you can see the hole in the in the photo, towards the foreground) that's not used for anything. So this way the throttle lever all the way up closes the choke, and the little spring opens it when you mow. Perfect. Sorry, I don't have a photo here of that spring attached. Total time: under 5 minutes.

    Bookmark   October 3, 2008 at 10:04PM
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I'm having a similar problem with my MTD rider. It has the 18HP B&S engine. I replaced the fuel filter and serviced the fuel pump. Still nothing. I will try replacing the solenoid and see if that's it. When I removed the top of the carb with the float and looked in the chamber there wasn't a lot of gas. I also noticed something with the fuel pump, the large spring and washer. If I put in the way it is in the diagram the engine won't even start on choke! If I reverse it it will run on choke and sometimes for 10 minutes but then dies.

So I'll try the solenoid and see what happens. I also looked at the vacuum line from the fuel pump to the block. It appears fine.

    Bookmark   October 5, 2008 at 7:24PM
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A friend and I finally looked at my lawn tractor. It turned out to be a combination of things. The spring and washer inside the fuel pump were turned the wrong way. We replaced the fuel hose but it was still okay. He believes that the float was hanging down too low and the pin that holds it was out of adjustment as well.

There is no fuel solenoid on this engine. (It's an 18 hp B&S 422700 series). I got the coil just in case but it's not needed. The machine is now running excellently!

This is a 16 year old MTD and is built very well. I sorely wanted to save this machine.

    Bookmark   October 20, 2008 at 8:06AM
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My Deere L108 is dead. I flipped the mower on its side to remove blades for sharpening. While undoing the spark plug boot, which was slightly corroded, I stripped the connector off of the coil's wire by mistake. Anyway, long story short - the engine won't start. New coil is in place. Starter is fine. Battery may be a touch on the low side. Haven't tested the spark yet (assume it is OK). I didn't want to overdo it on the starter, although I did the standard + battery to bolt on starter; it works, as it also does with a boost from jumper cables connected to a car. But it seems that either the engine isn't receiving fuel, or the spark is missing. I'll pull the plug tonight to see if there's anything in the cyliner. Don't smell raw gas, but that could just be my imagination. Could it be that I somehow damaged one of the safety switches or a section of the wiring harness when I flipped the tractor on its side?

    Bookmark   October 30, 2008 at 1:50PM
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I'm thinking a bit more about it, and it very well might be a fuel issue. After I righted the mower, air probably managed to get into the fuel line. I'll check the cylinder for residual oil (from when it was on its side), spray a blast of carb cleaner in there, clean the plug, close her up, shoot some carb cleaner into the carb, cross my fingers, and hope she starts.

    Bookmark   October 30, 2008 at 2:07PM
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Runs for 15 -30 minutes under load. then quits. will idle for an hour. If after all your engine cks' fail ck your mower deck.I found out almost 30 yrs ago the hard way. even had the shop ck it out.I couldn't mow more than 30 -40 min tops and it would die down and stop .the shop hit me up for a short block. well the old engine was beat .but that wasn't the problem. the idler pully on the deck was going bad. once so hot it would start to seize and drag down the engine. next time the engine starts to die out stop and ck how hot the pullys are on the deck. The new plastic one melt down ,the old steel one don't

    Bookmark   October 31, 2008 at 10:06PM
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OK, here's a photo of the spring I installed on my to keep the choke open except when I push the throttle lever ALL the way up to choke it. I drilled one little hole in the plastic housing for the left connection for the spring.

Here is a link that might be useful: Photo

    Bookmark   November 9, 2008 at 8:44PM
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Tractor, Craftsman 917.581, Engine Briggs 18.h.p, 31H777
What are the settings for valve clearance?
Starter has been replaced, new battery, tried jumping directly to starter with new, fully charged battery, but engine will onlly move to compression stroke. This problem has been intermittant.

    Bookmark   November 24, 2008 at 10:04AM
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berely, you need more than just the settings for valve clearance, you need the procedure as well. If you DO NOT follow the required procedure, your compression release feature will not function. Click the link below and read the thread. Pay particular attention to the posting by walt2002. Contact walt by e-mail (it's given in the post) and get the complete "step by step how to". Please start a new thread outlining your situation if you need other help (an old thread like this does not always get everybody's attention).

Here is a link that might be useful: more about valves

    Bookmark   November 24, 2008 at 12:14PM
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Hi everyone, great info for the DIY. I had the same situation with a 16hp B&S. It would run for about 1 hour and quit. I ignored the problem and paid the price, the engine blew, which brings me to my current problem. I was able to replace the engine with exact model# engine: model# 326431, type# 0020-04. Replace it and it was running good, just needed minor adjustments. Before I could enjoy it, it would not start. Came to the conclusion that it needed an ignition coil. Replaced it, got good spark, but it is hard to start and it needs the aid of starting fluid. When it does start it runs REALLY bad, like its misfiring or starving for fuel. But it can be starving for fuel because now it leaks from carb. as you try to start it, especially when you stop turning it over the fuel just keeps leaking for a few seconds. All I did was replace the coil. Any advice out there, thanks

    Bookmark   December 6, 2008 at 4:12PM
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I'm assuming the engine is used and had sat for a while. looks as tho a good carb and fuel line cleaning is needed. Replace the bowl seal and float valve whilst you are there. An inline fuel valve and new fuel line is also a good investment for these. If the fuel overflowed, it may have entered the crankcase - so the oil should be changed if this occurred. In the future, it is best to start your own thread.

    Bookmark   December 7, 2008 at 1:32AM
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Hello People, I notice that this topic has gone on for Years. Back in Sept. of 2007, Famousron had SUCCESS, by not adjusting the out-of-adjustment valves. HOW can this be? The Valve LASH was TWICE what the Spec. called for ... Super loose. I need to know what Adverse effect this has on the engine, and what Problems it would cause. Thanks, Jim.

    Bookmark   February 8, 2009 at 9:21AM
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"I notice that this topic has gone on for Years. Back in Sept. of 2007, Famousron had SUCCESS, by not adjusting the out-of-adjustment valves. HOW can this be? The Valve LASH was TWICE what the Spec. called for ... Super loose.I need to know what Adverse effect this has on the engine, and what Problems it would cause."

Well that depends on WHAT engine. Super loose will not work for an OHV B&S unless it is worn out.

Walt Conner

    Bookmark   February 8, 2009 at 11:32AM
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As I was not present when the valve lash was checked, nor have I seen the feeler guages that were used........I can not confirm the reported values or performance of that case in point. :^) Adverse effects of "valves out of adjustment": Valves with too much clearance will result in excessive noise (clicking & tapping), will cause the engine to "de-rate" or operate at less power than designed for, will cause "impact wear and/or damage" of the rocker arm and valve stem ends (hammering effect), and in some engines.....will cause the compression release to be less effective (or not effective at all). Generally speaking, excessive valve lash causes an engine (of any given displacement) to operate as if it was actually a smaller displacement engine. When excessive valve lash exists, the valve timing is affected in 3 ways. The valves open late, close early and the duration span is shortened. Because of this, valves with excessive lash DO NOT allow for complete aspiration to occur, and so the engine never inhales a full charge of air & fuel on the intake stroke, and on the exhaust stroke.... the engine does not push out as much of the exhaust gasses as it could if the valves were in proper adjustment. Valves with insufficient lash: Valves with too little lash can result in loss of power as well, but for different reasons. I need to refer to each valve separately on this. Too little lash for an intake valve will result in THAT valve not sealing to its valve seat. During the compression stroke, this causes a drop in compression for that cylinder because the leakage of compression will be backward into the intake manifold. During the power stroke, combustion gasses can leak back into the intake manifold. This is detrimental to the performance of engines because the combustion gasses raise the temperature of the incoming air/fuel charge AND reduce the available oxygen in the air/fuel mix. This effect is more like "insufficient fuel" than a lean condition because the volume of material (fuel and air) is modified by "inert" combusted gasses instead of simply having too many oxygen molecules in the mix (as would be the case of "lean mix") Exhaust valves with too little lash will result in absolute destruction of the valve (and consequently, the engine) due to the valve overheating. The exhaust valve cools itself in 2 ways. The minor way a valve cools is through conduction of absorbed heat upward through the valve stem where it can be shed into the valve guide and to the lubricating oil above the guide. Some "exotic" exhaust valves are made with hollow stems filled with Sodium to increase cooling by this means. When this type of valve heats up, the Sodium liquifies and as the valve moves up and down, the liquid Sodium is thrown to the top portion of the valve stem where the heat is absorbed by the lube oil in the valve compartment of the engine. The major way all exhaust valves keep cool is through contact of the valve margin to the valve seat. The design intent is for the valve margin (part of valve face that contacts valve seat) to press tightly against the valve seat during the intake stroke, compression stroke, and power stroke. Being in contact with the valve seat for approximately 540 degrees of crankshaft rotation (in the case of 4 stroke cycle engines) provides enough time for the valve to shed some heat into the valve seat and cylinder head (both at the valve seat and in the valve guides). Being seated against the valve seat actually reduces the amount of heat the valve, valve seat, and valve stem is subjected to by only exposing the valve face to combustion during the power stroke. If the valve has too little lash and is unseated during the power stroke (this is when the combustion process yields the highest heat), the combustion will leak past the valve into the exhaust passage and heat the valve margin, the valve seat, and the valve stem which induces a much greater amount of heat into the valve than would have occurred if only the valve face was exposed to the combustion. Because the valve is now absorbing too much heat and has no way to shed the heat (below a safe level), valve destruction accelerates. The now superheated valve will actually grow longer, which only makes the leakage and heating worse. Soon, the combustion gasses will begin to erode and wash away material from the valve margin and valve seat. Superheating of the valve can cause the valve to crack and break. Superheating can cause the valve seat to loosen in the cylinder head. Superheating of the valve can cause the valve stem to seize in the valve guide. If this happens, kiss this engine goodbye. The stuck valve will be struck by the piston and after that, it is pretty much guessing as to what happens next, but you can bet it will be something terrible involving a piston, crankcase, and cylinder head.

    Bookmark   February 8, 2009 at 1:33PM
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It depends on how you define "success".
Fixing a problem that wasn't valve related by not adjusting the valves?
Runs great, runs decent, runs adequately....
A lot of that is in the eye of the beholder. Running "steady" after dealing with the engine quitting every 15 minutes would seem "great" to me!

Most tractors are so "overpowered" that the loss of a HP or 2 is probably never noticed. We're talking about engines that are in the 20 HP range, when mowing probably takes 1/2 that. Unless you have the engine putting out it's rated HP AT high speed, it really doesn't need to "breathe" at 100% anyway!

    Bookmark   February 8, 2009 at 6:31PM
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All true Bill. I want to add here what I left out in my long post above. The scenario with the "stuck valve being struck by the piston", does not occur in "flat head" style engines. Only in overhead valve engines can the piston make contact with a valve.

    Bookmark   February 8, 2009 at 8:08PM
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Mr Conner could you please send me the instructions for adjusting the valves for my 31p777 model 0296?
Ed Jackson
shipmaster at fuse dot net

    Bookmark   March 18, 2009 at 11:27AM
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My situation is a little different, buy I'll post nonetheless since earlier in the thread someone wrote that no one ever came back with feedback, and this thread is one I read while I was troubleshooting.

I repowered my JD with a brand new engine, old one (350777-1134) didn't have an anti-fire solenoid. New engine (350777-1159) does have it.

Installed the new engine, had to swap out a couple of parts off the old and onto the new to make everything nice, fired it up and it ran great in idle.

Whenever the throttle was advanced, the engine would increase in rpms, then start hiccuping, and want to stall. I never let it stall because I'd always pull back the throttle before it did.

Showed every sign of fuel starvation.

First thing I found was that the clamps on either end of the the impulse tube were never installed up/down over their respective nipples. I reset those, no change.

The fuel filter was an opaque plastic, so I swapped my old clear plastic filter in its place. When at idle, there was a dribble of fuel coming into the filter, it never pooled. A minimal flow in.

Checked for kinks in the fuel lines, etc, etc.

Finally pulled the front off and removed the anti-fire solenoid. When the key was turned, it gave a nice "click" and it actuated. But not knowing how much movement was needed I left it off the carb and reset the bowl onto the carb with a plug screw.

By the time I made it over to take a peek at the fuel filter, it was full of fuel.

Fired the engine up, it ran fine at all throttle settings.

Took the anti-fire solenoid to the JD shop, they gave me the condescending "stupid homeowner" speech that these guys are ever so famous for, then after bench testing it they admitted it was indeed faulty.

I'm going to cross-post on my original thread as a "how it went" follow-up.

I'm no mechanic, so the info on this forum helped quite a bit. Thanks!

    Bookmark   April 26, 2009 at 6:42PM
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Had this problem with a new Snapper 20 hp briggs after about two months. Ran fine some of the time then would start shutting down after ten to fifteen minutes of running. Checked everything on engine imaginable. Also filter, fuel line, and even siphoned and replaced fuel. Finally in next year decided to give up and take back to the dealer but took off the fuel tank( which is under the seat and a pain to get out) and thoroughly examined it first. Found a couple of small plastic shavings left over from manufacturing loose in the tank. Cleaned out, replaced, and a year and a half later still running smooth as a whistle.
It was a fuel problem,but not an engine problem of any kind. Got to believe this is what most of the problems mentioned here are.

    Bookmark   May 16, 2009 at 11:25PM
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i have a briggs&stratton 18 hp 42a707 when you start it will run all day when you shut it off it will not start. you let it set overnight it will start and run all day. can anyone help me with this problem? thanks

    Bookmark   May 22, 2009 at 10:11PM
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    Bookmark   May 28, 2009 at 2:04AM
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"i have a briggs&stratton 18 hp 42a707 when you start it will run all day when you shut it off it will not start. you let it set overnight it will start and run all day. can anyone help me with this problem? thanks"

You don't say if it won't turn over or if it spins but won't fire.


Please don't use all caps. You need to do some checking yourself. Have you checked for spark when it quits? Have you checked for fuel flow when it quits? Have you checked to see if you can turn it by hand when it quits?

Might remove the gas tank cap and see if it still does it.

Walt Conner

    Bookmark   May 28, 2009 at 8:13AM
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the spark its blue it turns over just fine, has a good gas flow to the carb the thing will run fine. when you kill it it dont start can try to boost it with a car it will turn over fine,it will hit like it trying to start but it will not start.

    Bookmark   May 30, 2009 at 3:09AM
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dirtmover: Check the spark before and after to make sure it is the same.( before you run it, and then after it quits and won't restart) also you may want to just replace the spark plug if you haven't already. I have a Briggs single 11hp that suffered from a bad coil that would only act up after it got hot. Then it would not restart until it was cool again, and repeat the cycle all over again. Mine did not stall out, but badly misfired once it was hot. I found a procedure to check the coil from B&S website and it was bad, so one new coil later and it was all better. What year do you have? first two digits in the code number on the shroud.

    Bookmark   May 30, 2009 at 8:13PM
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dirtmover_375, Thanks for you help i bought a new coil put it on today it works like a new one now.Thanks for all your help. Its a 95

    Bookmark   May 30, 2009 at 11:12PM
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18HP, Mod 42A707, type 2238-E1, code 0008095B

I just got an older 42A707 mounted on an MTD tractor; vintage 2000. It has the problem of dropping off after some run time but the problem I am addressing first is it running lean. It has a manual choke and some choke must be maintained for it to run smoothly with power. I think that the RPM fall-off after some run time is caused by the engine not being able to respond to governor demands. The carb does not have an accelerator pump and the governor demand is too fast for the lean running engine to cover. After all the normal checks, filter changes and a new fuel pump kit, it has improved but still requires some choke at all speeds. The carb is nonadjustable so the only things left are the float level or a new main metering jet. Does anyone know if a range of metering jets may be available for this unit?
thanks in advance.

    Bookmark   June 3, 2009 at 1:04PM
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1) best to start a new thread. OP will get unneeded copy of this reply post.

2) 10 yr old machine... might start with verifying the fuel cap vent is working right.. then remove/clean fuel tank well.. then replace fuel line(s) and replace current fuel filter with new correct fuel filter.

3) if still trouble, check/replace fuel pump. If carb was acting up, would think it would start happening right away.

    Bookmark   June 3, 2009 at 2:32PM
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I have an 18HP Briggs engine, Craftsman lawn tractor model # 917.273399 and am experiencing the 15 minute run then shut down scenario. I let it sit for 15 minutes then resume cutting for maybe 10 to 12 minutes. I have done the following:

Changed air filter
Changed oil and filter
Changed Fuel Filter
Cleaned grass/debris from engine
Changed spark plug

I still have the same problem. My next step is to remove and inspect the carburetor. Any suggestions??

I have noticed that the V belt seems to have a lot of slack, could it be contributing to this problem? I can't find any info in my manual on adjusting that belt, anyone have any info on it?



    Bookmark   August 21, 2009 at 8:52AM
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pete78, your next step should be to inspect the fuel tank cap vent hole for being clogged. A clogged cap vent can produce the exact problem you describe. Nothing inside the carburetor will cause the sypmtoms. A straightened paper clip makes a suitable probe for cleaning out the vent passages in the cap. Probe both the outside hole and the inside hole of the cap. Compressed air is also useful in blowing out debris in the vent feature. If your problem persists after this, create a new thread to address your particular machine and this problem.

    Bookmark   August 21, 2009 at 12:34PM
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Thanks for the info. The last time the mower quit I removed the gas cap and it would not start, so I don't think venting is the issue. The diameter of a paper clip is too wide for my cap but I will try a staple. I checked the resistance of the coil secondary circuit and it was 5,000 ohms which is within spec per briggs.

Any input on adjusting the V belt?

    Bookmark   August 21, 2009 at 4:39PM
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i have two mtd tractor mowers with identical briggs and stratton 18 hp twin ii i/c model number 42a707. one of them sounds like the battery is dead but i just bought the battery yesterday. i cant figure out what the problem is any one have any ideas?

    Bookmark   April 11, 2010 at 6:39PM
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best to start yer own thread - this one's a cuppla yrs old and won't get much attention.

    Bookmark   April 11, 2010 at 7:16PM
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I have 18hp craftsman tractor, single cylinder, 31H777, 0202E1 03. The mower runs for 20-30 mins, sputters and eventually stops. If I wait for it to cool down it will run until engine becomes hot. It starts easy when cold and not so easy when hot, often backfiring. I've changed the fuel filter, checked the gas cap, had the carb flushed and new gaskets by local lawnmower mechanic last summer. after reading thru the forum I'm starting to believe the valves maybe out of adjustment. Help is appreciated. scvol

    Bookmark   August 7, 2010 at 3:49PM
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scvol - one thread is enuff. You're just going to keep those who really try to help from doing a decent job.
And, this is an old thread (like 4 yrs old). Stick with the other new thread you just started.

    Bookmark   August 7, 2010 at 6:03PM
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I share everyone's frustration with the Briggs and Stratton engines. I have a B&S 16.5 HP OHV (Model 313707) on a Gardenway riding lawn mower (2002) that I've struggled with for a couple of months. I mow about 6 acres with this mower pulling an offset 60 inch trail mower. It's not all flat ground either. So it's turned over hard for several years but I just dealt with it. I kept a new battery in it and sometimes had to put the charger on it if it sat a couple of days. Recently though, it would only run about 10 minutes (not even pulling the trail mower) and then shut down. It was strange though, if I pulled out the choke it would run a little but not much better and subsequently stall. So I would turn the key off and then restart it and it would run a couple more minutes. I would do this several times until it wouldn't restart. As the battery wouldn't have time to charge and was turning over so hard I would end up sticking the charger on it. Ugh!

Let it sit an hour in the shade and then run again for 10 minutes.

I replaced:
Fuel lines
Fuel filter
Air cleaner
Ignition Coil (Took it back after it didn't help)

I cleaned:

I adjusted the bracket on muffler to get it so the exhaust pipe went into the muffler far enough. It wasn't going in very far as it always bumps into stuff. I replaced 1 bolt that was missing from the exhaust pipe.

Because I was so irritated by pushing the mower back to the garage I decided to try to at least get the stupid thing to turn over easier and hopefully it would fix the stalling problem. I went to this guys video (See URL) on YouTube and he shows you how easy it is to adjust the valves. I took all the sides, front panel, and hood off and followed the instructions on YouTube. I didn't bother putting the mower back together as I just wanted to see if it helped.

Holly crap, it ran great, I mowed for 2 hours, it runs quieter, it turns over smooth. (Flat ground 70 F.) I though that I just bought a new motor.

2 days later I put everything back together, hooked up the trail mower and started mowing. However, it was 85° F. and by no means flat ground. It ran about 10 minutes and died.

Evidently, the gas in the mower is getting heated up with all the heat retained in the engine compartment and worse on hot days. The stalling worsened when I would mow on a sideways slant.

The guy earlier in this thread noted that he glued the rubber part of the anti spark solenoid back onto the knurled piece of steel. I decided to just take it off and run it without the rubber part. It was loose and not working correctly. I can replace the solenoid later.

I hooked up the trail mower and mowed for a couple hours on an area that I have to ride the fender of the mower to keep it from tipping over. This was the best test as this is usually when it stalls.

I think it's fixed and I hope someone benefits from my learning experience.

    Bookmark   August 20, 2010 at 3:05PM
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What exactly is an "anti-spark solenoid"?

    Bookmark   August 21, 2010 at 12:28AM
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hi i have a b&s 18 horse twin cylinder and i have no spark. replaced coil. still no spark. plugs are good. set gap on coils with buisness card. no spark. no points under flywheel just the big round magnet thing cant think of its name at moment. ? is. is there anything else on here that can cause no spark? i even unplugged the earth wire from coil still no spark. is there a way i can check coil with meter? also the guy i got it from said he replaced the starter is it possible to get a starter that spins the engine backwards? it cranks good and fast like it should ? there is what way is it sposed to spin. any help would be great thank you. jason

    Bookmark   August 21, 2010 at 2:05AM
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Jason Ford has created a separate thread to address the above issue.
Please do not continue the discussion in this thread.

And Jason, posting in multiple threads DOES NOT increase the chances of your finding a solution.
The same members who might help you will be reading all the threads and posts, you are reaching the same "audience".

    Bookmark   August 21, 2010 at 11:44AM
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I was trying to find help, with my Murry 18 hp lawn tractor and I was amazed and dumbfounded, when I found this link discribing the exact same nightmare problems, that I have been having with mine.
I had attempted to rebuild the carb, about eight years ago, with a kit and it ran okay for awhile, but now I'm having problems getting it started and to keep it running.
My problems are;
Over heating and the engine stops running, Will not run smooth, unless the choke it pulled out, about an inch, Back fires, after I turn the engine off, always cleaning the plugs.
I'm 66 and not to good at repairing engines, without a detailed manual.
I have tried to read the posts above to see if I should be looking for a new mower.
I bought a new Briggs & Stratton rebuilding kit online Sterns 520-080, as a last attempt and have been putting off rebuilding it.
I would appreciate any tips on how to proceed, for someone, that is in way over his head.
Thanks, Bert

    Bookmark   September 6, 2010 at 2:15PM
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looking up your Stens kit, I see you have the old flat head twin.
On the bottom side of your carb should be a hex plug
that can be removed with a 5/8 wrench. Remove it.
Crank the engine, and fuel should pulse out, and hopefully
any crud/water/dirt that may be in there.
Then take an Allen wrench, 3/16 I think, and stick in the hole and remove the jet inside and clean it, crank the
engine some more and let some more fuel/crud pulse out.
Re-assemble, it should run a lot better.
The after-fire bang is something different, another unrelated topic.


    Bookmark   September 6, 2010 at 4:42PM
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I have a similar problem with a 28q700 series that has just started after 12 years+ of use. The mower stalls after 30-60 minutes of use. It can be saved by using full choke for a few minutes. The fuel filter is always empty at this point and I know when it is going to happen by watching it emptying.

Checked filter, cleaned fuel lines and fuel cap.

If I wait for the filter to slowly re-fill I can get another 30+ minutes.

Mower runs perfectly before problem. No surges , no misfiring on steep slopes etc.

Did we reach and final conclusions on this?

    Bookmark   January 15, 2011 at 9:19PM
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Hi all,
I was able to get it running using a car fuel filter which proved the filter installed was wrong. The service shop had installed a filter for a fuel pump version not gravity feed. Installed right filter the problem is resolved.


    Bookmark   January 19, 2011 at 5:05PM
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Hi and HELP :) I have a B&S Model# 406777 20hp and theres something going on.. I have one of 2 oil fouled spark plugs with black oil. The other is ok. The dipstick is showing full and clean oil. Starting is very hard and when it does fire, I get a bellow of blue grey smoke and then it is clean. It will run plowing my driveway for around half hr then it just dies as it has no gas but it is full of fuel.
Give it 10 min or so to cool off and it fires right up easily but runs for only 30 seconds or so enough time to park it again.

I have replaced the fuel filter, air filter, gas line, spark plugs, but it still isn't behaving.

PLEASE help, we are expecting a lot of snow this week and I am an older guy. Thx for your help.

    Bookmark   January 31, 2011 at 10:41AM
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Harry, your troubles might be caused by one of two very different things.
The part of your description about the 30 minute run could be caused by the gas cap vent orifice being plugged (but this scenario would not explain a fouled plug).
Remove the cap and probe into the vent hole with a paper clip wire to break up any material that might be preventing the tank from venting air in as the fuel is depleted.
Try to probe both the outside and the inside hole. If you have compressed air, blow out the vent holes after probing them.
The second possibility (and this would cover the plug fouling) might be that one of the magnetos (ignition coils) is breaking down after a period of use.
You need to try and determine whether the cylinder with the fouled plug loses its spark when the engine dies.
The "oil fouled" spark plug might not be oil fouled (but I can't see it from here) at all. It might just be wet with fuel after it loses its spark.
I also recommend that you create a new thread of your own to cover this issue. It was OK to present your problem in this thread for a beginning, but it would be best if you make a new thread now as issues of this nature might easily turn into a long thread all to itself.

    Bookmark   January 31, 2011 at 11:08AM
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18hp briggs. Sucks all oil out of crankcase after 30 minutes. I think time to rebuild any ideas

    Bookmark   April 4, 2011 at 1:34PM
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Need help with 18hp briggs, it runs at full rpms.

    Bookmark   April 5, 2011 at 12:21AM
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Hi i hav a b/s 18.5 intek Plus rider dlt 3000 model 917 275820
I got this from a friend and the vales had backed Off so far a rod came loose. They stopped using it and i Put it back together but im getting blow back thru carb, is the motor screw or is there something i can do to fix. If i hold hand over carb i take it will pop a lil so it gets fire and gas but im lost pretty much now.

    Bookmark   May 22, 2011 at 11:30AM
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Dear all. I had all of this also with a mount field tractor mower. Seemed to run lean, lose oomph and then stop after ten minutes or so. Then start again you gt the drill. B&s 11.5 hp. Noticed that it used no fuel to speak of! So I noticed that tightening the inlet manifold bolts seemed to suck petrol through more effectively. I read through the above, reset the valves, renewed the carb but same problem. Could have avoided it all by disconnecting the fuel line to see if petrol was flowing. Turns out a a plug of grass and dirt was obstructing the fuel line! Cured!

    Bookmark   May 29, 2011 at 6:19PM
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Okay I screwed up and ran engine for a couple of minutes with the blower cover off, apparently causing the motor to overheat and stall. Afterwards, I checked the compression on both cylinders and both were close to 100 psi. Pulled the cylinder head covers on both cylinders and both the valves and piston seem to be undamaged. Engine will sound like it's trying to fire but doesn't run. Only thing I do get is repeated back firs which scare the heck out of the neighbors. Checked the spark on both plugs and both seem fine. What else should I be looking at that may have been damaged by the engine overheating. This engine has been in storage for years and I recently repaired the starter. Once I put the starter back in it started right up. Now I want to kick myself for running it without the blower assembly in place. Thanks for any advice.

    Bookmark   June 13, 2011 at 8:13PM
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Hello, My model 31H777 18 HP Briggs is popping back through the carb just off idle and gets worse as rpm is raised. Engine will idle smooth but has no power. Valve lash set at spec, fuel filter replaced, spark plug replaced, air filter replaced, fuel solinoid working properly, coil gap at spec. Flywheel key not sheared but I am going to pull the flywheel for a closer inspection. Compression is 170 PSI. Muffler is flowing (not plugged) but is suspect for back pressure. Any other ideas are much appriciated. Thank you.

    Bookmark   June 15, 2011 at 1:13AM
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Posting to an ancient thread (hijack) seldom returns the proper attention that a new, separate thread on the new subject machine would get.
Case in point: The previous 5 posts before Scott got no responses, and there are several more posts in this thread that went unanswered since 2006 when this thread originated.

    Bookmark   June 15, 2011 at 10:30AM
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this engine has internal timing and not anything such as flywheel only rules taking it out, the timimg gear internally has sheared to governer, you may see a broken spring to govener externally, over time the shear increased to hitting more objects, this is internal problem and not generect carburation problem, the valves screw up due to this timing it governs the governor and everything. I found it slightly sheared and my system went to crap. These guru's on internet just fix easy stuff. Later

    Bookmark   June 18, 2011 at 2:04AM
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I also have an 18HP Intek engine, on a Craftsman LT200 Lawn Tractor (917.273758) that I bought in 2004. Towards the end of last season it started surging and stalling after I refueled the tank. I figured it was probably old/bad gas. I had it serviced after that and it worked fine for the last couple of cuttings of the year. This season it worked fine for a couple of cuttings, then started acting up again intermittently. I cleaned out and checked the carb, didn't see anything there. After restoring everything, started it up and it ran fine sitting there. This morning I started cutting the grass, and after a couple of minutes it started acting up again. I found this site, and read all the posts. I went with the solenoid theory, and unscrewed it to test the mower. The little plastic/rubber cap on the top of the solenoid came right off. I left it off and re-installed the solenoid w/o the cap. The mower ran fine for the hour+ of the cutting. Later, I may try gluing/epoxying it back on, but that cap WAS the PROBLEM

    Bookmark   July 17, 2011 at 3:50PM
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I Have a Briggs Stratton Murray 18 HP engine that after it has been shut off it wont start after getting hot.
If anyone knows what is causing this please let me know .

    Bookmark   July 26, 2011 at 1:48PM
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Ray, if you took the time to read this thread every time it needed to cool down, it would have time cool down and run! Best start a new thread. If it cranks but doesn't start, it is likely a funky coil.

    Bookmark   July 26, 2011 at 10:53PM
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Had the same problem of running for a while the it seemed starved for fuel. replaced the thing sticking out of the bottom of the fuel sediment bowl with a short 8mm fine thread bolt and a washer. mowed three hours today with no problem. Thank you guys for all the help

    Bookmark   August 1, 2011 at 7:07PM
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i purchased new motor 18.5 hp briggs intec plus model 31p777.after install motor runs fine but doesent have full range of rpm's idles fine but at full throttle it is only slightly above idle . the throttle cable works fine could this be governor related if so how to adjust?

    Bookmark   September 27, 2011 at 7:47AM
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I have a carb linkage problem and need assistance.

The B&S 31P777, 0296-E1 engine on my 6 year old lawn tractor failed to start (first time ever). I checked fuel pump, spark and got the engine to kick-over and run briefly when directly injecting carb cleaner into the intake.

FYI, the lawn tractor sat in the garage for 5+ months through our Texas drought and 100 deg F summer. Thinking my problem was old gas and varnish build-up in the carb, I took off the carb and cleaned it. Now I am having trouble with reinstalling to see if I have solved my original problem.

The "link-choke" rod fell off the "bracket control" assembly and I cannot figure out it fits back on.

Does anyone have a link to, or an illustration of a bracket control assembly that shows how the link-choke rod is mounted in the assembly?

Thanks in advance for your time and support. BK (aka Phread)

    Bookmark   October 29, 2011 at 12:35PM
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The most common used is the single throttle/ choke control style. This one the rod is directed back from the choke shaft with the hoop end being fed though a slot on the control bracket. When the control is pushed towards the choke mode, the flat tab on the little arm in the bracket pushes on the loop end of the rod thus closing the choke.

    Bookmark   October 30, 2011 at 2:13AM
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Posted by fisher40037 (My Page) on Mon, Sep 6, 10 at 16:42

looking up your Stens kit, I see you have the old flat head twin.
On the bottom side of your carb should be a hex plug
that can be removed with a 5/8 wrench. Remove it.
Crank the engine, and fuel should pulse out, and hopefully
any crud/water/dirt that may be in there.
Then take an Allen wrench, 3/16 I think, and stick in the hole and remove the jet inside and clean it, crank the
engine some more and let some more fuel/crud pulse out.
Re-assemble, it should run a lot better.
The after-fire bang is something different, another unrelated topic.
Fish Thank you so much for this post I just solved a 4 year old headace that had been getting worse after a carb rebuild. My Home built Backhoe is now running like a charm thanks to you Fish. Briggs 18hp vtwin off of a Crafsman riding mower is powering my hoe like it has never done before.

    Bookmark   November 1, 2011 at 11:21PM
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Please bear with me gentlemen.I'm widowed and don't have a clue as to the problem.Here's the story.My tractor wouldn't turn over although it sounded as tho it would.A guy hooked up my battery charger but shortly thereafter,the charger began to smoke.I actually thought the guy transposed the positive & negative.I hooked up a new charger and the tractor started.It ran for about 4 days w/o a problem.I was the one using it.A guy wanted to help me out and used the tractor.After turning it off,it wouldn't start.He continued to try to start it.Another guy tried and told me that the starter was smoking.I put a new starter on it a yr.ago and I have a hard time believing the starter is bad.It's not the battery cuz I had it checked.I read,in this thread,that someone had problems with the coil.How can I be sure the starter is bad and not the coil or visa versa? I know you guys are probably irritated by me asking what seems to be a small problem but after all I was kinda forced into learning how to use my tractor.Take note,I never have a problem when I'm the one using it.My problems seem to happen when it's others who use the tractor.I do use a trickle charger during the winter so I don't have a problem starting the tractor in the summer. I'm appreciative of any help you can give me.Thanks so much.

    Bookmark   November 29, 2011 at 4:59AM
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bargainhunter -
1. lending out yer tractor is like lending out yer checkbook or yer wife - proceed with extreme caution - at best.

2. we need some facts on what make/model of tractor you have, also engine make/model/type...
3. remove battery - clean battery cable connections - take battery to shop that can do a LOAD test and hydrometer chk.
4. post back in a new thread your info/results - this one is getting old/too long.

    Bookmark   November 29, 2011 at 8:14AM
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As to the riding mower that stalls sputters and dies after 15 minutes I probably have the solution. This happened to me and any post I seen was telling me the gas cap was clogged, all this technical other stuff that was obviously just to confuse someone because they didnt have a clue what was wrong. At one point I remembered when the mower was new, when I turned the switch to the on position I heard a clicking sound. This was the fuel solenoid located on the bottom of the carb. I unscrewed it to see if it was gummy and it wasn't so I screwed it back on and still no clicking. I decided to order one and it was between $45 and $55. Then I researched what it does and it simply cuts the fuel off to carb when you stop the engine. So I bypassed it, don't think a professional would tell you to do that and I'm not either but I had already put an in-line cutoff on my mower because when I am finished, I simply turn the in-line valve closed and in 30 seconds or less the engine dies and no fuel is in the carb to get gummy. If you dont have a cut off valve you will need to clamp your fuel line off before you remove the solenoid, simply unscrew the solenoid and replace it with a short bolt. If you can't find a bolt then you may do this. I found a rubber washer like whats in a faucet repair kit about 1/16 and I used a leather punch to make the hole larger in the rubber washer. On the solenoid you will see a small black cap on the end of the needle, remove it and the small metal washer. Slide the rubber washer on the solenoid and that makes enough space so the needle doesn't cut off fuel in the carb. So no matter if the solenoid is working or not bypass it because even if it is working, they tend to get stuck closed after engine is hot. Bypass it and your mower will run just fine!

    Bookmark   July 20, 2012 at 12:55AM
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What is this solenoid supposed to do? How can you just take it off and the engine still operate? :^)

    Bookmark   July 20, 2012 at 12:50PM
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Mownie, he must have placed it in the cup holder. i'm pretty sure it just must be located somewhere on the tractor to work...

    Bookmark   July 20, 2012 at 11:34PM
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That must be it.

    Bookmark   July 21, 2012 at 12:25AM
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the fuel tap on the fuel tank can be removed, on the end of the tap is a filter, replace this filter. I had this issue and by process of elimination i found the root cause. Hope this helps someone out there, I know its a old posting from 2006. Goodluck

    Bookmark   December 18, 2012 at 5:40AM
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i have the vanguard b&s 18hp v-twin engine with pull start and was given to me recently,but it is in a few pieces.
what i am having trouble finding is a workshop/repair manual.
what i need to find out is where the parts around the throttle/choke and covers go.
its missing the starter motor and one of the pawles for the pull start.i think this must be an older type engine as i cannot find any numbers stamped on the engine block.
i really do need help.

    Bookmark   December 19, 2012 at 5:25PM
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I looked for your e-mail in your profile and saw it was not there.
If you want a manual e-mail me.

    Bookmark   December 20, 2012 at 12:33AM
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thanks heaps mownie.i really appreciate your help.

    Bookmark   December 21, 2012 at 7:44AM
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i found this starter on ebay,does anyone know if it will fit ?
or is it a different part number ?
if its not right,would anyone in australia have one they dont need ?

thank you

    Bookmark   February 5, 2013 at 1:14AM
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hi. i have a briggs 407777 0128 e1 991101yg with nikki carb
runs fine but the engine losing power and starts smoking when pto is turn on and engine rpm are brought up half way and sometimes it works fine for a few mins.
carb been rebuilt complete all new parts other then float, valves check, fuel cab taken off, changed fuel pumps, coils have been check with putting a differnt one on. any other ideas briggs dealer doesnt know what to do with it and neither does briggs tech people

    Bookmark   June 21, 2013 at 3:45PM
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Needs a cam

    Bookmark   June 22, 2013 at 1:03AM
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I'm having a problem I replaced the fuel pump diaphragm because I was getting bad gas flow but now the fuel pump isn't drawling and pumping gas at all does anybody have any ideas that I can check? I even put the old diaphragm back in and it won't work the little bit that it was.

    Bookmark   May 22, 2014 at 10:39PM
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Create a new thread of your own making to address the issue you are having. This thread is simply too old to be adding to.
In your new thread, include the engine model and type numbers you find on the engine.
I feel you might have chosen this thread because you have an 18 horse Briggs, but you have no idea how many different 18 horsepower Briggs engines there are with different styles of fuel pumps. The model and type numbers will be pin point precise on the engine and parts.

    Bookmark   May 23, 2014 at 12:22AM
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