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17HP Intek - no compression release?

bgpeters
15 years ago

My JD barely turns over (B&S Intek OHV 17Hp 31F707 0112E1 030115ZE)... basically stops spinning on every compression stroke. At most I can get a backfire out of it (I now think it was probably caused by the spark generated on the exhaust cycle firing on the unused gas). My first thought was my battery was not delivering so I replaced it with a new 300 CCA - no improvement.

I was happy to read on this forum it was likely either my valve clearances or gas leaking into the cylinder causing hydraulic lock.

I have confirmed that there was no gas in the cylinder and that gas is being delivered to the carburetor.

I am getting good spark.

I have carefully set my valves to .003-.005 Intake and .005-.007 Exhaust after the cylinder has gone down 1/4" after TDC.

Still no improvement.

After reading here about the compression release arm in B&S engines that should prevent the intake from closing all the way at low revs (start up) I decided to measure when the intake valve closes (from what I understand the reason we set the valve clearance on a B&S 1/4" after TDC is because this release arm should be interfering with measurement of arm clearance earlier in the stroke. On my engine, the valve is solidly closed at TDC and for about 90 degrees before (i.e. my feeler gauge slides in anywhere in this arc before TDC - just like the at the position where the adjustment is to be made).

At this point I'm guessing that this little compression release arm is messed up somehow and my next step is to pull the engine and open it up... is there anything else I have missed? Is this the next step? I've always thought my engine doesn't spin up as well as it should, but now it's hopeless.

Thank you for any input.

Barry

Comments (22)

  • mownie
    15 years ago

    Barry, don't begin taking your engine apart yet. In fact, wait until Walt C. (or another "Intek experienced" member) has a chance to address your problem. I downloaded the Briggs I.P.L. and the Operators Manual PDF's for your engine and from the illustration of the camshaft, this particular Intek might NOT HAVE "compression release". In the I.P.L. for your engine there is no "compression release bump" shown in the drawing of the camshaft (but this might just mean that Briggs did not include it in the drawing). To make a comparison, the Briggs IPL for a Vanguard engine clearly shows the "compression release bumps" on the base circle of the intake lobes of the camshaft. The component that you called "little compression release arm" is actually the "valve rocker arm". All typical 4-stroke cycle, pushrod engines have 2 rocker arms per cylinder (whether a compression release is provided or not). One way to confirm if this engine camshaft has the compression release "bump" would be to set-up a "machinist's dial indicator" to measure the movement of the intake valve rocker arm during the "compression stroke" of the cylinder. If this engine has the "CR bump" on the cam lobe, you will observe a rise (brief) of the pushrod as the tappet encounters the bump, followed by a lowering of the pushrod as the bump moves on past the tappet.

  • walt2002
    15 years ago

    "My first thought was my battery was not delivering so I replaced it with a new 300 CCA"

    This is typical reaction.

    "I have carefully set my valves to .003-.005 Intake and .005-.007 Exhaust after the cylinder has gone down 1/4" after TDC. Still no improvement."

    "At this point I'm guessing that this little compression release arm is messed up somehow and my next step is to pull the engine and open it up... is there anything else I have missed?"

    This engine does have a compression release arm on the side of the cam gear and it typically does not show in the IPL. The Vanguard utilizes a totally different method.

    This series of engine does have a history of the cam lobes not being hardened properly and wearing out prematurely. Some people have gotten this warranted even though their warranty period is up. Some of these have also had the compression release lever, primarily the spring on it, fail. Look at the amount of movement of the rocker arms. If the camshaft lobes are worn out, there will be little movement and perhaps the Intake not nearly as much as the Exhaust.

    I am sending you something that may help, a final test before tearing down. Sorry, I do not have B&S Customer Service number, should be able to find it on the Internet. You local Service Dealer is likely to say, "NO" to warranty.

    Be aware that IF you get a new camshaft, it will likely not look at all like your old one and you will wonder if they sent you the right one.

    Good luck.

    Walt Conner

    To see if the compression release is working on B&S Intec engines, remove the spark plug. Remove the valve cover, turn the engine flywheel clockwise while watching the valve action. When the Intake Valve closes, stop. Now focus very closely on the valve spring retainer of the Intake Valve, continue turning the flywheel clockwise. In about 1/4 turn, you should see the Intake Valve Retainer (and valve) make another little move towards full closed. This indicates the Compression Release is working. IF you see no movement, try again. Still no movement, there is a problem in the Compression Release system. When the engine is cold, you can rest the side of your hand on the head and grasp the Intake Valve Spring Retainer between you thumb and index finger while turning as described and you should be able to feel the Retainer move.

  • mownie
    15 years ago

    My apologies to Barry and other members, my thanks to Walt for explaining the differences between Intek and Vanguard style of compression release mechanisms. Now I'll just sit back and read (probably less harm that way).

  • bgpeters
    Original Author
    15 years ago

    No problem mownie.

    I just got done doing Walt's recommendations...

    I removed the spark plug and valve cover. After the exhaust stroke I watched the intake valve open and then close (about 1/4 turn before TDC). At that point the lifter arm has a gap of about .004 at the valve stem. I continued turning clockwise keeping my fingers on the end of the lifter where it would contact the valve stem. At no point after it closed did the lifter again even touch the valve stem until the next intake stroke began. I went through the stroke sequence 3 times to be sure. I can't feel the lifter ever touching the valve stem again after it closes on the intake.

    So it sounds like I need to replace the camshaft. Not too happy about that.

    Are there any pitfalls I should keep in mind and avoid as I proceed with pulling the engine off and pulling the whole thing apart? If I'm reading the I.P.L. diagrams correctly it looks like I should be able to do it by
    1) drain the oil,
    2) remove the engine
    3) remove the oil sump
    5) lift the camshaft out (looks like it's driven by a gear on the crankshaft) - nothing pressed in to deal with in I hope?
    6) drop the new one in & close it up with new gaskets.
    7) enjoy a properly functioning engine again.

    Again, any input is very welcome. Thank you for all your help.

  • walt2002
    15 years ago

    "At no point after it closed did the lifter again even touch the valve stem until the next intake stroke began."

    The rocker arm doesn't touch again, the idea is that the valve stay open a few thousandths until this point, not close then reopen.

    I always advise people to buy a Repair Manual for this series engine, about $15 - $20. Sounds like you pretty well have the idea - note - IF this engine has an oil pump, remove round cover and the pump from the bottom of the sump before reinstalling sump, then re-install pump and cover.

    Walt Conner

  • bgpeters
    Original Author
    15 years ago

    Oh. I was expecting that the rocker arm would pop the valve open briefly to release some compression before TDC. Opps! I misunderstood.

    So what I have to look for/feel for is the valve seating a final few thousandths before it reaches TDC. I sure could miss that very easily. Sounds like the compression release arm somehow impedes the normal valve movement independant of the push rod/rocker arm. Interesting. I wish I could see it on the I.P.L. I'll check for this when I get home tonight. Now I understand why using a feeler gauge is recommended. Without a feeler gauge I doubt I will be able to detect this (which I don't have)... but shouldn't I be able to use the rocker arm tip to detect this change in valve position with a feeler gauge? It would seem that the gap between the rocker tip and valve stem should be a few thousandths greater when the valve is being prevented from fully seating (>.005) compared to the gap at 1/4" below TDC (.003-.005)?

    If it turns out that the compression release actually is working when I re-check focusing only on movement of the valve stem tonight. Then, I suppose my start problem must be a worn out starter.

    I've got gas, spark (spinning without the spark plug in), I think the flywheel key must be OK since the valves seem to be opening & closing at the right places in relation to TDC (it seems), the starter just barely gets the motor past the compression stroke - certainly not with enough speed to initiate a reasonable spark.

    Thanks for your help Walt in keeping me on track.

  • bill_kapaun
    15 years ago

    "Without a feeler gauge I doubt I will be able to detect this (which I don't have)."

    It doesn't take too much additional clearance for the compression "bump" on the cam to not engage.
    Buy (or borrow) a feeler gage set. They aren't that expensive and even a cheap set will do.

  • walt2002
    15 years ago

    "So what I have to look for/feel for is the valve seating a final few thousandths before it reaches TDC. I sure could miss that very easily."

    Not if you follow my directions, I am an old man with vision problems and I can see it and should be able to feel it though I never tried that actually.

    "Sounds like the compression release arm somehow impedes the normal valve movement independant of the push rod/rocker arm. Interesting."

    No, see below.

    "Without a feeler gauge I doubt I will be able to detect this (which I don't have)... "

    Well you are going to need a feeler gauge to set the valve clearance at some point unless you hire job done, but shouldn't need to do what I said.

    "It would seem that the gap between the rocker tip and valve stem should be a few thousandths greater when the valve is being prevented from fully seating (>.005) compared to the gap at 1/4" below TDC (.003-.005)?"

    No, just the opposite, No clearance as it holds the valve a few thousandths off its' seat via the lifter-pushrod-rocker arm.

    Walt Conner

  • walt2002
    15 years ago

    I guess I could have explained a little farther but my posts tend to get long.

    The compression release mechanism on the side of the cam gear has a longer arm, a pivot point and a short projection past the pivot point. When the engine isn't running, a spring holds the arm "inward" and the short projection elongates the Intake Valve Cam Lobe holding the Intake Valve open a few thousandths of an inch. As the engine starts, centrifugal force causes the longer arm to swing outwards over coming the spring force and retracting the short projection returning the cam lobe to normal function.

    Anything that interferes with this action including excessive Intake Valve clearance, broken or dislodged spring, a bur on the side of the mechanism catching, dislodged pivot rivet, will prevent the compression release from working as will a cam lobe that has worn down too far.

    Walt Conner

  • bgpeters
    Original Author
    15 years ago

    That was exactly the problem. It spins nicely now.

    Now I'm trying to figure out how to get gas flowing again through the fuel pump. I must have it hooked up wrong.

    Anyhow I'm getting close to have it running again.

    Thanks!!!

  • walt2002
    15 years ago

    "That was exactly the problem. It spins nicely now"

    What was exactly the problem?

    To prime pump, get gas flowing IF hooked up right, remove gas cap, wipe off filler lip, place mouth tight against and blow (do not inhale)

    Walt Conner

  • bgpeters
    Original Author
    15 years ago

    I followed your instructions to watch/feel from some minor intake valve movement in the compression stroke, and finally decided that there was absolutely none. It seated and that's all. So I removed the engine and opened it up. The spring that is on the compression release arm was doing nothing at all, so the arm was always flying away at any RPM, or just never closing. I order a new Cam Shaft, etc.

    Now the engine spins as it should for starting (it used to come to a complete stop on the compression stroke), and so no start.

    Thanks for the tip on getting the pump primed. I'm going out to do that now.

    The throttle linkage seems a bit mystical. I hope I have it on right. I think I have the choke linkage right.

  • bgpeters
    Original Author
    15 years ago

    That did it. It's running!! Yahoo!

  • davie1973
    15 years ago

    HI TO ALL......THERE IS NO COMPRESSION RELEASE.STARTER WILL ONLY GO UP TO THE COMPRESSION STROKE ONLY.THEN IT STOPS.HAD STARTER CHECKED BY SHOP AND IT WORKS OK.SET VALVES AT 3-5 ON INTAKE AND 5-7 ON EXT.BUT STILL THE SAME,DOES ANY ONE HAVE SOME INFO ON WHAT I CAN DO.THANKS FROM AN OLD 67 MAN

  • bill_kapaun
    15 years ago

    WHAT engine?
    Model & Type-

    Did you adjust the valves with the piston 1/4" PAST TDC?

  • walt2002
    15 years ago

    The preceding posts on this list should answer your question IF you have a B&S single cylinder OHV engine. Email me for test of compression release.

    Walt Conner
    wconner5 at verizon dot net (put in proper format)

  • njdpo
    15 years ago

    interesting ... the spring was wasted... was the cam wasted too ?
    Or did you decide to go through the motions with a new cam because you were already there ?

    thanks - Curious dave.

  • davie1973
    15 years ago

    ok i will email you, but if you read this check your email.......here it is. briggs #313777 17hpv. type-0135-e1,code-011030ze. this is what i have done so far,new battery,new solenoid,the starter was checked by shop,it still won't go past the compression stroke. so took out the sparkplug and broutht to tdc on the comp. stroke. +1/4in past.measured with small screwdiver.set valves as follows,int at .003 and ext at .005.adjusted to specs.still the same thing, but i will try to see if there is any movment of the int.valve before tdc. thanks

  • davie1973
    15 years ago

    ok walt.i did what you suggested!i reset the valves again.iput a gauge on it reading was 28...i did notice that when the intake valve closed,then it come back down alittle,then went back up.....then i came to the compression stroke,it started to compress and then it stopped,then started compressing again.any hints or more tests. thanks to all.....marry xmas to all, james

  • 1929Marmon
    10 years ago

    Have read 17HP briggs - no compression release

    My unit starter turns fast. Will start if choke but idles very slow then stops, take out of choke stops. Is it possible compression release stuck in compression release mode, Also have lots of back psi out of crank case with dip stick out. Blow by makes me think blown piston or rings, but no oil on plug or gas.

  • mownie
    10 years ago

    Post the engine Model number and Type number you find on the engine. Those specifics are needed on this issue because Briggs uses 2 very different styles of compression release.
    One style has a mechanical compression release that COULD BE subject to failure, but the other style is simply a specially configured camshaft "grind" that has no separate moving parts save for the camshaft itself.
    Your symptoms actually might be more an indication of a blockage in the carburetor main jet circuit than a possible problem in a compression release.
    To test whether this issue might be due to a fuel deficit, try pouring a couple of spoons of gasoline directly into the carburetor throat and then cranking the engine.
    If the engine seems like it wants to run well (for about 2 seconds) on this amount of gas, your problem is in the fuel system.
    Your other symptoms (about "blow by") might lean toward a possible leaking/blown head gasket. But what you think is "blow by" might only be normal "displacement" caused by the up and down cycles of the piston. When you remove the dipstick, you defeat the crankcase vent system and that might be misinterpreted in the puffs coming out the dipstick tube.
    There are a couple of ways to check for blown head gaskets.
    You really ought to create a new thread to cover this instead of trying to handle it this way (riding on somebody's old thread).

  • codyw_churchill
    7 years ago
    last modified: 7 years ago

    I have the same engine and I am having the same problem as the original post but SOMETIMES if we jump it with a car battery and we have the fly wheel in the right position it will start. Could this just be the starter? I am getting 12v on the load side of the solenoid so I know its not the solenoid. Im just not sure that it is the cam or the compression release spring if once we get it started it runs fine.. Anything would help. Thanks

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