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Knocking sound after rebuilding top end

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2008 crf250r, in the process of finishing up a top end rebuild, and after installing the timing chain onto the cam I deciding to hand crank the engine slowly with the kickstart to see if everything was alright. There is a distinct knock that sounds like it is coming from somewhere in the cylinder each time I turn the engine over. What would be causing this sound? 

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The de-compressor mechanism makes a 'knock' once every second turn when you slowly rotate the crank,

either by the kickstart or by hand when turning the hex to line up the index dots.

 

In the case of a freshly rebuilt engine, you should have initially slowly rotated the engine by hand rather than the kickstart lever

to check for binding, without the extra leverage of the lever it's less risky of bending a valve if the cam timing is off.

Edited by mlatour

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So its a normal thing after rebuilding the engine? Or did i mess something up?  Sorry, kind of new to this...

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Depends on what's making the noise, if it's the decompressor yes it's normal all the time,

noises caused by other things no, perhaps post a video.

 

I'm guessing you're not following the instructions from a service manual either?

Special assembly procedures, torque specs, clearance/tolerances etc.

all sorta 'important' in an expensive 13000 rpm race engine....

Edited by mlatour
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