06 crf450 hard to kickstart after shimming valve

Have a buddy who just had valves done on his kids bike. Had a local mechanic with some experience with 4 strokes reshim valves. Now he says it's hard to start, because of high compression? Says he has to get it past tdc to start it.

Told him to check de-comp adjustment. He said it is within spec.

Going to have him bring it to me so I can check it, de-comp is my first thought. Anyone else ever come across this??

timing out 1 tooth for sure, the decomp kicks in 2 late, seen on a few bikes now were the chain is getting a little stretched and people cant decide which tooth to set it on. put money on it!!

^^^^I would say the same thing.

.. not sure if the decomp mechanism is the same as the 04crf450.. but if so and it is found to be timed correctly, look at the spring on the far right side of the decomp lever on the end of the camshaft. When you remove the valve cover, you can catch the end of the small spring with the valve cover gasket (if it is stuck to the valve cover like it usually is). This will have the decomp lever spun out all the time (and as soon as you kick not) when it gets above 600 rpm. Had that happen to me once..

This will have the decomp lever spun out all the time (and as soon as you kick not) when it gets above 600 rpm. Had that happen to me once..

Can you clarify that?

Joe

Can you clarify that?

Joe

the decomp is cetrifigully operated. When the cam spins, the lever moves into a position no longer applying decomp to the valves. It is held in place when kickstarting however by a thin wire spring that holds it "in", then above 600rpm or so (once the motor begings to start) that is enough revolutions that the weighted small lever flips outward no longer in the decomp positon. Well, if the spring is off, the lever will be flipped outward with any revs, and the decomp won't be applied at all.. YOu would need to see a pic of the end of the cam to fully understand perhaps..

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