It is on a mower. Going great but would not start again after stopping for a short time. Suspected sticking valve as every thing else checked OK. Removed tappet cover to find exhaust valve has a 1/4 inch tappet gap. The inlet seems tight. How could this happen to what seemed like a good healthy engine. Has something slipped inside. Any ideas. It has little compression and just backfires when injected with 'start ya bastard' (either).
40wav,
Jan 21, 1:16am
Have you checked the shear key on the fly wheel! If it's done its job, the timing will be out and make it backfire.
noodle34,
Jan 21, 1:55am
it may have dropped a valve seat
mugenb20b,
Jan 21, 1:59am
Broken cambelt.
40wav,
Jan 21, 1:59am
Sorry, I read 'it has a little compression'. I agree that it has probably dropped a valve seat. I had one that did this and I just tapped it back in a gently punched around the edge (with a dot punch) to make it stay there.
NZTools,
Jan 21, 2:11am
I'd love you to show me the cambelt on an 11hp B&S.
the-lada-dude,
Jan 21, 2:19am
do you idle the engine for 40 + seconds b4 shutting down ! this is the 4 valve FIengine NZ TOOLSso of course its got a belt drive.
mugenb20b,
Jan 21, 2:24am
I was joking.
falconer,
Jan 21, 3:43am
Thanks for the replies. The flywheel key is OK. The head is difficult to remove without engine removal so I was looking for something easy. The huge tappet gap I think will have something to do with it. The cam belt and turbo timer are OK. I had not given them a thought to start with.Great ideas. Keep them coming. Thanks. I will check the electronic valve lifters while I am at it.
falconer,
Jan 21, 6:43am
Thanks for the ideas. noodle34 was right . I jerked the head and there was the exhaust valve with it's seat at a weard angle. This explained the 1/4" tappit clearance. Tapped it back into place and am about to centre pop it and put it back together. Thanks again for your ideas.
dunwoody,
Jan 21, 7:50pm
Mower engines are very prone to overheating which lets the valve seats move, this is usualy caused by clogged cooling fins.
falconer,
1 day, 15 hours
Good thinking dunwoody I hope the seat dropping was cause by something but the cooling fins looked ok with very little junk around them. I have always regarded Briggs & Stratton with suspect and I still regard them as a resonably reliable highly inefficiant very crude engine. I read somwhere one sidevalve mower engine gave 30 times more emisions than a late model car.
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