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Mystery stall....

982 Views 2 Replies 2 Participants Last post by  TW_in_BC
This happened to me again over the weekend...has happened a few times and the build up is always the same:

Riding along...then make some sort of last minute course-correction (taking a different trail, etc)...lug the engine a bit...a few pings...dead.

Then, when I go to crank her's as if there isn't even a piston. Cranks over VERY fast (almost as if there is no compression at all) but won't start.

Sit down for a few minutes and let her recover...start her up...away I go.

As I said, this has happened once or twice before and I don't know WHY she sounds the way she does when I try to re-start.

It's a mystery.
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Whoa... sticking valve? Not sure if you want to do this with a hot engine, but next time ya might pull the plug & test for compression. With something other than your thumb of course.

I'd guess a sticking exhaust valve would keep the piston from inhaling enough fuel/air mix from the intake valve. And then the stuff would just be pushed out the exhaust valve and there would be nothing compressed for the plug to ignite.

If it's a bent valve, it could be catching part way open when hot, then letting loose when it cools. It might just keep moving while the engine is running fast, but have a chance to stick when slowed down due to lugging the engine.
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