How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Curtis B. Your Own Question
Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 25648
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
Type Your Small Engine Question Here...
Curtis B. is online now
A new question is answered every 9 seconds

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: 2 months ago.
Category: Small Engine
Expert:  Curtis B. replied 2 months 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.