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Decompressing with engine running.


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On my '97 250 will I have damaged any valve gear by inadvertantly pulling in the decomp. lever instead of the clutch lever when my bike was lying on top of me still running.

Thinking back I think my engine loud tappet ticking happened shortly after this occurred.

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+1 with what Chuck said. That should not have caused you any problems.

Personally I don't like using it to kill the engine when there are other methods, or using it like a Jake Brake on long downhills. I think chronic use of it in those fashions can cause wear and mushrooming from the hammering the parts take.

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It's meant to be used while the valves are moving..... since it's intended purpose is to allow for a compression release in the motor while you are trying to pop start the bike or kick it over.... so it shouldn't do any real harm pulling it while it's running. It's no different than pulling it and cranking the bike through with the kick lever, only the motor is moving a lot faster.

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I had an XR600 engine on the bench 4-5 years ago. The owner had been using the manual decomp lever to slow down and while decelerating going down hills. The tab on the RH exhaust rocker that the decomp lever in the cam cover pushes against had broken off and found its' way into the bottom of the engine. It is amazing how much damage this little piece of metal caused. Chips from the tranny gears had been thrown around inside the case causing a lot of havoc, the worst of which was a damaged thrust washer on the rod big end necessitating a crank rebuild. I wouldn't use the decomp lever to stop or slow down the engine.

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Yes the decomp is intended for use while the engine is turning, but while it's being kicked and not at a running rpm. Having said that, occasional use of the decomp while the engine is running should not cause problems but regular use will eventually do what TrailRyder said.

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