Thread: '08 crf 150r
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Old August 28th, 2018, 07:18 AM   #12
jkv45
Rev Limiter
 
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Name: Jay
Location: WI
Join Date: Jul 2013

Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes

Posts: A lot.
MOTM - Jun '18, Oct '16
Haven't pulled the head off yet, but I'm pretty sure of what I'll find. When these, and many other race 4-strokes, are over-revved on downshift or no load the cam gear/hub will spin on the cam. It's pressed-on and not staked or tacked apparently. Usually that puts the valves in contact with the piston.

If you don't know it and reassemble everything with the timing marks lined up the valves will still hit, or if it's not enough to make contact the bike just won't start. So even though this one had the cam messed-up, I'd still need to replace it most likely. At least I know it.

Had some time at work, so I powder coated the pipe heat shield and valve cover in a gold texture powder very similar to what Honda uses on Magnesium covers.




Last futzed with by jkv45; August 29th, 2018 at 06:46 AM.
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