Hello, I'm stumped and could use some help.Have a model #28S700 13hp OHV. This motor recently threw a rod due to gas in the oil. Replaced connecting rod,had crank ground,replaced counter-weight.Piston and cam seemed OK.Also replaced fuel solenoid and float valve. Engine initially started with difficulty and ran extremely rough with muffler getting red hot while backfiring out of carb.Replaced intake valve and lapped.Now will not run at all,but backfires out of carb.Checked valve clearance OK. What is with the compression release being on the intake valve? I've only seen them on exhaust.It seems to me this is causing the problem but...any ideas? Thanks!

what about other things, cam and crank lined up on timing marks? flywheel keys good? sure the valve clearance is right? also was the float checked out? wasn't heavy or sloshed?

I appreciate your reply. Yes cam and crank lined up, even tore motor back down to verify. New flywheel key and timing gear key.Checked and rechecked valve clearance intake is .004 exhaust .006 at 1/4" past TDC on compression stroke.Float is good.I should also note that compression measures 60 psi, I would think it should be higher but with compression release I'm not sure. Poured kerosene into manifolds before attaching head to verify valves sealing,all good. Spark plug is getting very wet.

what about rings? where they put in right?

Did not replace rings as all looked good,no cylinder wall groove or scoring.Did pressure test and no leakage. Also checked for head warpage-none.I've noticed that at the compression stroke on the way up the intake dwell is extended about.025" then closes when the piston is about 2/3 of the way up. I'm assuming this is the normal function of the compression release.The exhaust valve is closed until just before BDC of the firing stroke.

weren't lined up was more of what i meant i guess, though i don't think so, have you read the compression turning it backwards? as for its type of compression release, really have hardly any idea for a ohv if its like a side. probablly someone else would know more on that, just havn't had any ohv's to work on yet.

As far as I can tell from the B&S IPL, this engine does not have a mechanical compression release. This means that the "compression release" is actually handled by the valve timing and that you have probably timed the valves on the wrong stroke. Don't worry though...I've done it more than once.

yeah i went to look at it to earlier, nothing mentioned.

The compression release on this motor is handled by a flywieght type mechanism mounted on the cam gear next to the intake lobe.At cranking speed the lifter rides on this mechanism for part of the cycle,as speed is increased(ie engine starts) the mechanism moves out of the lifter path. I'm going to go check it out in a minute.Also will check flywheel key since at one point the flywheel was loose.Thanks for the input!

Well I finally got it running. I'm a bit embarrased to say it was the flywheel key.Somewhere between the initial rough running and discovering the intake valve was bad I sheared that brand new key. Gotta laugh I guess,sure did waste a lot of swear words though:) Sure do appreciate the feedback-great sight!!

backfiring out the carb sounded like a sheared key :lol: it can be the simpleist of things.