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Force 90 lost compression

J

John Neptune

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I have tested compression and

I have tested compression and have only about 20 lbs in the top cylinder. The engine still starts and runs as long as I keep the rpms up. Is there an easy diagnosis (valves vs rings) or does the unit need to be torn into before the diagnosis can be made?
 
" You might want to pull the h

" You might want to pull the head, that way you can look at the head, cylinder walls and the top of the pistons, and evaluate the damage. You might luck out and have only a blown gasket. "
 
I occasionally hear it backfi

I occasionally hear it backfire during cranking prior to actual starting. Isn't that an indication of a burned valve?
 
" The only valves in that moto

" The only valves in that motor are the reed petal valves, which is part of the fuel system. You could have a timing problem causing the backfire. With that low compression I would certainly pull the head. "
 
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