This engine ran just fine when it was put away last fall and now it wil barely start. When I get it started, it back fires through the exhause every once in a while and if I pull one plug wire the engine stalls completely and if I pull the other it makes no difference. I took the head off of the dead cylinder and the valves are fine. They were set correctly and the spark looks good. Same as the other side. The starter can barely spin the engine over against the compression in one cyinder. It seems like a timing issue but the magnetos are not adjustable and since it is on a riding mower, I don't think the flywheel key is suspect. I took the nut off and looked at it and it looks fine. Any ideas would be appreciated. Luckily we are having a heatwave here and the grass is not growing but it will rain one day and I will need this mower again.

 

Have you checked valve clearance?

 

Sounds to me like the carb needs cleaning.

 

Valve clearances are correct and I cleaned the carb again today. Really didn't find anything in either jet or the bowl. I drained all the fuel and put fresh fuel in and ran it for an hour but it is still the same. What baffles me is that when I pull one plug wire it stalls and when I pull the other it makes no difference in the engine speed. I swapped the coils and nothing changed, swapped the spark plugs and nothing changed. I don't even know what to try next. I'm stumped. It's a 23 hp engine and obviously not up to full power.

 

Sounds like a compression test is needed. If the dead cyl is getting spark and fuel there has to be a valve problem.
Mike

 

I agree,
when you pull the wire on the "dead" cylinder and it makes no difference cause it is not working, this is also why when you pull the wire on the other cylinder it dies cause then both cylinders are dead.
check compression like suggested. I would suspect a valve problem but you say the clearances are ok, but something is wrong??? let us know what ya find.

 

I sent it out. I will post the solution when I get it back.