What is the full model number of your engine?
My onan engine is conected to a Lincoln Ranger 8 welder generator.
The model number on the motor is P216G-1/11421H.
I have spark, compression and fuel but can't get it to fire. It does spit back through the carb so I think it may be timing. I'd like to make sure it is firing at the right time.
The timing is set by aligning the cam gear to the crank gear during assembly. There is no adjustment, and the only way for it to slip time is if physical damage has occurred inside the engine. The only way to verify timing is to pull the gear cover.
If your set is spitting gas out of the carburetor, you are more likely looking at too weak of a spark, fouled plugs, exhaust valve not opening, or a stuck float in the carb causing the engine to flood.
Did you check both cylinders for compression?
How did you check for spark - with an in-line tester or did you physically pull the plugs and verify the condition of the spark?
If you pulled the plugs, were they wet?
I would check all this out before pulling the gear cover - timing is the least likely cause of your set.
If you really want to pull the gear cover, click here for instructions.