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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 13581
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: 8 months ago.
Category: Small Engine
Expert:  Curtis B. replied 8 months 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 8 months 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 8 months 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 8 months 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.