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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 28339
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a Mcculloch mower & believe the engine is a 4stroke

Customer Question

JA: Hello. How can we help?
Customer: I have a Mcculloch mower & believe the engine is a 4stroke push rod 160cc Honda clone. It was running normal but backfired thru exhaust violently when shutting down.Now won't start & just backfires thru exhaust.Think decompression is jammed on .All other timing is ok.What do you think? Thanking you Graham M
JA: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?
Customer: YES have new fuel,shut-off valve open,fuel getting thru to cause backfire
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: I have partly dismantled engine ,have removed top cover after removing flywheel but cant see decompression mechanism & governor without total stripping which I am trying to avoid. Thanks for your help Graham M
Submitted: 1 year ago.
Category: Small Engine
Expert:  Curtis B. replied 1 year ago.

Flywheel timing key was ok? Check the valves , you may have valve that is not seating, due to rocker arm or broken spring. Do you have compression? Backfire is sign that valve is open when the spark occurs.