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FREAKZILLA

YZ400 lost power

11 posts in this topic

I just put a YZ400f motor in my atv about three months ago. Last night at an arenacross it all of the sudden lost power and the engine sounded like it was dragging really bad and the head pipe turned red about six inches from cylinder. I also could here compression coming through the air filter when I was trying to crank it. I'm thinking maybe a valve or two stuck open. Any advice would be appreciated.

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Does the motor still turn over ok? Does it still run? if it doesnt I would take the head off the engine and have a peek. See whats going on in there, thats really the only way to know whats up.

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Check the timing. A cam gear could have slipped on the shaft, changing your timing. Sounds like it could be the cause....

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