Hi everyone. I have a 2008 crf250r that blew up last year. It blew up because I didn’t put lock tite on the timing chain retainer bolt. It ended up sucking the retainer up in the timing chain and throwing the timing off, causing the valves to bend. Before the bike blew up it would only kickstart when warm. It was always super picky. I sent it to a shop and had the carb tuned. It definitely helped but it still wouldn’t kick start cold. Now I have rebuilt the motor with a new cylinder works cylinder and vertex piston. I also installed a brand new head with stainless steel valves. The head was a bolt on ready kit. The only thing I haven’t replaced (besides the crank which has no up and down play) is the cam. In theory, if I did it all correct, it should run the same as it did before it blew up but now it seems like the timing is a little bit off. I can hear the valves ticking a little bit. I have checked the shim specs 4 times and they are perfectly on when the motor is at TDC. The timing is also perfectly on. Can anyone try to point me in the correct direction? I am thinking the cam could be part of the issue but I don’t want to just start buying parts without knowing for sure. Thanks, Owen.
I had the same bike. Is the kickstart really hard to kick or more locked up feeling
Or will it kick fine but just not start
It has good compression and turns over well. It just will not start. You can kick it as many times as you want and it doesn’t even try to pop or anything. If you bump start it it fires right up. It used to idle good and run good after being bump started but now it will only idle super high. It seems like the valves are out of adjustment but they are perfect. I’m wondering if maybe the cam gear spun on itself and now it’s slightly out of time? The same thing happened on my 450 and caused it to be out of time. Got a new cam and it ran great. Just wondering if maybe it could be the same issue??
If the motor locked up, there is a very good chance that the cam gear spun on the camshaft. Your timing marks will still line up but the actual cam timing will be incorrect. You would have to check the cam timing with a degree wheel or if it moved far enough you could compare how it looks with another cam.
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Ok yes that’s what I’ve been reading on the internet. I think I’m gonna get a new cam for it and Intake valve buckets so they wear evenly. Thanks for getting back to me. I’ll let you know how it goes when I get it.
UPDATE
I installed the new cam today and adjusted the valves to spec. The bike started up 5th kick and idled perfect. I shut it off and started it right back up first kick. This is the first time it has ever done that during the time I have owned it (3 years). The only last question I have is, is there a break-in period on the new cam?
PS thanks for all the help.
Nice that it's fixed. No break in period needed for cams, but good habit to check the valve clearance after 2h or so to make sure it's still in spec.
Ok I will do that
Thanks again
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