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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 12592
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a 2 cyl. 20 HP Onan engine in a Stiener lawn tractor.

Customer Question

I have a 2 cyl. 20 HP Onan engine in a Stiener lawn tractor. I think its a mid 80s model. It starts missing and backfiring thru the intake as soon as you put a load on it. Engine has 1900 hours on it. I have had the carb checked and the valves lash set. Where should I look?
Submitted: 14 days ago.
Category: Small Engine
Expert:  Curtis B. replied 13 days ago.

Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!

Expert:  Curtis B. replied 13 days ago.

Model of engine? Does it have electronic ignition or points and condenser? If you run cylinder check, by removing one spark plug wire at a time, is it firing on both cylinders?

Customer: replied 13 days ago.
the model is a P220G-1/11162G Onan Performer 20 It has electronic ignition, it runs perfect until you load the engine, such as blowing snow, then it cuts out and backfires thru the intake.
Expert:  Curtis B. replied 13 days ago.

Is battery voltage to the coil constant, or could it be dropping? I'm thinking that coil is breaking down and spark becomes erratic. Service manual link above.