Return to the Tractors Forum | Post a Follow-Up

 o
slow crank ohv briggs

Posted by Scrambler69 e (My Page) on
Mon, Oct 14, 13 at 19:14

Model 31H777 Type 01151E Snapper Scrambler 16HP ZERO TURN Last time I mowed, I had to jump to get it started. Battery was old so I replaced it. I had the starter checked as good. Engine will only crank withe plug removed. Made several attempts to adjust valves with same result. TDC,compression stroke, set intake(bottom) lash to .003, exhaust(top) lash to .005. Have done my Goldwing lash several times but never a Briggs. Now, I have noticed when the engine cranks, on th engine pulley, the top belt also turns. The deck belt doesnt turn. This is my first zero turn mower and Im not sure if its supposed to or not. It seems to go to the top of the electric clutch. If anyone has any suggestions, I would really appreciate it. This thing is driving me nuts. Maybe I'm not finding TDC right or something, or I've got bigger issues. Last time I mowed, it ran great. Now the starter struggles to get past the compression stroke. Any ideas? .....been scanning youtube and some forums for advice, maybe I'm missing something. st.anger41 at gmail dot com


Follow-Up Postings:

 o
RE: slow crank ohv briggs

All sounds good except set the lash when the piston travels 1/4" past TDC. Yes, it is not uncommon for the traction belt to always spin on most zeros.


 o
RE: slow crank ohv briggs

Ahhh, hope thats it. Now when you say 1/4" past TDC, do you mean run the piston down 1/4"? So after TDC??? Thanks again, hope thats it!!


 o
RE: slow crank ohv briggs

Ahhh, hope thats it. Now when you say 1/4" past TDC, do you mean run the piston down 1/4"? So after TDC??? Thanks again, hope thats it!!


 o
RE: slow crank ohv briggs

Sorry for the double post. Went back and re-read my Briggs pdf, and it says to turn the engine counterclockwise??? A 1/4", so Im confused on wether its before or after TDC. I did my initial adjustments at TDC, so hopefully tomorrow I can git r done. Thanks again.


 o
RE: slow crank ohv briggs

Yes, after TDC using the normal rotation of the engine. It is done that way so the compression release does not interfere. When the gap on the intake valve increases, the compression release does not function as it should. While you are there, put a 10mm wrench on the base of the rocker studs so that you know that they are tight. Hopefully this adjustment will do the trick for you.


 o
RE: slow crank ohv briggs

I can send you detailed instructions on setting the valves plus a test for compression release/camshaft and a helpful hint IF you like. It is possible the camshaft is bad. Address below, put in proper format and remind me, engine model number and what you want.

Walt Conner
wconner5 at frontier dot com


 o
RE: slow crank ohv briggs

Thanks Walt,I tried again to set the valves with the same result. I sent you an email with the info I am needing. Im not sure what you mean by proper format, so I hope I did it right. But anyway,tried it 1/4" past TDC this time but the same results. I'm trying to figure out why my Briggs manual(pdf version) says to turn the engine counterclockwise??? I hope I'm just confused but my gut feeling says I've got bigger issues. Thanks to all who have helped here, Doug


 o
RE: slow crank ohv briggs

***" I'm trying to figure out why my Briggs manual(pdf version) says to turn the engine counterclockwise?"***
Interesting that you pointed this out, I had not actually noticed that the text says "counterclockwise".
But I can assure you that whether you actually turn the engine clockwise (as I have always done) or counterclockwise........so long as you go the 1/4" of piston descent after TDC on that compression stroke/power stroke (or vice versa) the valves and the base circle of the camshaft are still in exactly the same state with the same dimensional value, and thus your adjustment will be just as accurate.
Insofar as Walt's proper format....that means dot=. and at=@


 o
RE: slow crank ohv briggs

Mownie - You are no less than a teacher's teacher. Simply outstanding.


 o
RE: slow crank ohv briggs

Funny! I just looked at a tsb on Intek twins and they showed clockwise. In the service manual - Intek singles CCW as stated. One OLD twin Intek showed TDC. (Obsolete) The "updated" valve adjust bulletin for all engines: step 2. Continue to rotate crankshaft past TDC until piston is 1/4 in. (6.4 mm) down :)MAybe not updated enough...


 o
RE: slow crank ohv briggs

Ok, thanks all. I have more problems than a valve adjust will cure. Using Walt's info, I have found that the compression release is not working. I will have to figure out which way to go now...probably tear into it but not sure when. Feel free to chime in if anyone has any tips on a cam check/change but im not sure how soon I can tear into it. Thanks again all.


 o
RE: slow crank ohv briggs

Replace the camshaft. A good "winter time" project (if you have winter in your area) :^)


 o
RE: slow crank ohv briggs

The cam replacement is straight forward. The worse part is getting the engine and peripherals RnR'd. You could verify that it should crank better by sliding a feeler gauge at the intake tappet and cranking.


 o
RE: slow crank ohv briggs

The feeler gauge trick will not work to verify a worn out camshaft if the compression release "high spot" (on the base circle) is worn away.
The feeler gauge trick can verify if a valve with too much clearance is preventing an otherwise sound compression release from being effective.
But if the high spot on the base circle is wiped out, adding feeler gauges may keep the valve from seating through the entire compression stroke, which would of course lower the compression pressure and allow the engine to spin.........but it would not verify a worn out camshaft.
Adding feeler gauges to the valve stem/rocker in the case of a worn out camshaft would have the same effect as simply adjusting the valve lash to the point the valve can't seat.


 o
RE: slow crank ohv briggs

Really the purpose is to help duplicate a compression release enough to get a better idea on the quality of the starter. "Starter checked as good" usually means someone at a parts counter threw a jump box on it, it went round and round displaying some torque. Well, if it were a Ford starter...That leaves interpretation to the counter person in most cases. It can also hopefully allow the OP to get the engine to up and run, bolt the cover on and mow the grass.


 o
RE: slow crank ohv briggs

OK, I missed the finer points of what you were implying Tom.
Yes, that would work to prove whether the starter motor was capable of spinning if the compression was reduced somewhat.
I took it as meaning that the feeler gauge trick would confirm a worn out camshaft. My bad :^(


 o
RE: slow crank ohv briggs

I would check the amount of movement of the Intake Valve. It should move about the same as the Exhaust and should be in the range of 3/8". IF it does not move that much, suspect defective cam lobe worn down due to improper hardening. IF the Intake does move about the same then suspect the Compression Release Mechanism has failed, both common.

Either way, you would need a different camshaft. Note I did not say NEW camshaft. I would look for a junk OHV 28 series or a 31 series engine. There are plenty of them out there due to thrown rods. IF your engine has an oil filter, you will need a camshaft from one with an oil filter. IF yours does not have a filter, you can use a camshaft from with or without a filter. Be sure to check the camshaft for damage, bent, bad lobes. Also, check the Service Manual for instructions on installing sump IF you have an oil filter - Oil Pump Drive Instructions.

Walt Conner


 o
RE: slow crank ohv briggs

Wait a minute, "shimming" the intake valve or adjusting to stay open could allow me to get it up and running to mow? I thought about that but didnt want to burn valves or create more troubles. I have an acre to mow and if I could get one last mowing done I could park it for the offseason and find a camshaft. I also thought about the drill method, but wasnt sure if an 18V Dewalt drill would overcome the compression.....and yes the starter was just checked out by a lawnmower (Snapper) dealer although beforehand I took it p apart, cleaned it, checked brushes, etc....it really looked pretty clean inside. So if there is a way I could get this up and running, Id be done for the season anyway, just dont to create more problems.......thoughts????


 o
RE: slow crank ohv briggs

Wait a minute, "shimming" the intake valve or adjusting to stay open could allow me to get it up and running to mow? I thought about that but didnt want to burn valves or create more troubles. I have an acre to mow and if I could get one last mowing done I could park it for the offseason and find a camshaft. I also thought about the drill method, but wasnt sure if an 18V Dewalt drill would overcome the compression.....and yes the starter was just checked out by a lawnmower (Snapper) dealer although beforehand I took it p apart, cleaned it, checked brushes, etc....it really looked pretty clean inside. So if there is a way I could get this up and running, Id be done for the season anyway, just dont to create more problems.......thoughts????


 o
RE: slow crank ohv briggs

I should clarify, by shimming, I mean adjusting my valves, then leaving the feeler gauge in the intake while cranking?? Wasnt sure how much oil Id lose. Ive been wondering if there was a way to allow me to get one last mowing without causing more damage. Love forums like this, lots of knowledge here!!!


 o
RE: slow crank ohv briggs

Thinking about what your compression release does- it holds the intake valve open ever so slightly as it nears the top of the power stroke.You can create your own with a feeler gauge and then once started, the valve will close normally. So, if you feel that you can safely do this, get it started and the cover back on - there probably isn't anything to lose. I've not seen a compression release lever break off and do other damage in my world. I also, ashamed to admit it- over tightened an intake for a customer who " was going home to mow 1 more time and then it was going straight in the scrap heap"! Not allowing the intake valve to close just CAN"T make it any happier...


 o
RE: slow crank ohv briggs

Hmmmm, I cant get the starter to crank any faster with this test. Had them adjusted at .003 intake and .005 exhaust. Adding my .003 feeler gauge between intake valve and rocker doesnt produce any better cranking...also tried adjusting to zero lash (wont run it like this, just a test) and still will only crank with plug removed...both valves have equal movement but I certainly cant see any extra movement in the intake valve after it closes to see the compression relief is working......when i did this, i had a good battery and went straight to the starter post to eliminate solenoid/wiring etc.... does this verify my starter is toast? This thing is driving me nuts!!!!! Lol


 o
RE: slow crank ohv briggs

***"had a good battery"***
Meaning that the battery has been load tested by a qualified testing person?
Have you tried connecting a set of booster cables to the tractor battery and a car battery?
Adjusting the intake valve to zero lash and THEN adding .003" feeler gauge at the valve stem "ought to" decompress the cylinder enough to allow the engine to spin with the spark plug in place, provided of course, the starter and battery are good.
Connecting a car battery with booster cables would eliminate a deficient battery from the equation and give an indication of where to go next.
The fact that you are not observing a rise of the intake pushrod pretty well confirms camshaft worn out.
Intake valve adjusted to zero lash and a .003" feeler gauge on top of the valve stem should permit the engine to spin and display a visible "back flow" into the carb. Do not do this with the spark plug cable connected.


 o
RE: slow crank ohv briggs

The battery is brand new and I keep it topped up with a battery tender. I suppose I can take it in for a load test. But I have also used it in conjunction wih a booster. I will try the zero lash plus the feeler gauge as I would like to see this thing spin.


 o
RE: slow crank ohv briggs

Leave your lash set at .003 . There is no need to create a no gap situation as it gets to operating temp.. You don't want it to start popping back through the intake. The goal is to slightly open the valve to release compression to crank it. Try a ..020 or so.


 o
RE: slow crank ohv briggs

Ahh....makes more sense now. i havent done anymore to it, intake is still set at .003. I borrowed a mower and
Made my last mow for the season. Ive pretty much comfirmed I have no compression release so Ill tackle the cam job this offseason as the mower is still in great shape....itll probably be awhile but when I get it back starting well Ill try to post here, so it may help anyone else who reads this post in the future. Thanks again for all of the great advice!!!!


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Tractors Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here