can a sprocket spin on the camshaft

ryanh827
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ryanh827
Edited Date/Time 12/26/2014 4:24am
i have a a 2009 crf 450 the sprocket on the cam is pressed on not bolted the bike locked up a few month ago jumped timing and bent valves bought all new valves and a new head used the same cam now the new motor wont start just pops but its in time perfectly and it test perfect on leak down but has no compression when timing marks are lined up but if we put the timing off one tooth it has compression so my question is has anybody ever heard of the sprocket spinning on the cam making out of time when the mark is lined up
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Paw Paw 271
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Paw Paw 271 12/20/2014 6:07pm
12/20/2014 6:07pm
The earlier CRF250R's had an issue with the pressed on cam gear spinning on the cam. It can be checked with a degree wheel and a dial indicator and the factory spec's for the cam timing.

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MotoX85
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MotoX85 12/21/2014 12:14am
12/21/2014 12:14am
YES, almost guarantee that is your problem. Have had many 250s do this.
BobPA
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BobPA 12/21/2014 8:59am
12/21/2014 8:59am
Yes, I had a 250 Kaw do this.
ryanh827
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ryanh827 12/21/2014 10:12am
12/21/2014 10:12am
thanks for the replys i guess ill be buying a cam tomorrow

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ryanh827
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ryanh827 12/21/2014 10:13am
12/21/2014 10:13am
MotoX85 wrote:
YES, almost guarantee that is your problem. Have had many 250s do this.
just curious how did you figure out that was the problem
Dragoo168
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Dragoo168 12/23/2014 4:20pm
12/23/2014 4:20pm
You could have also put the engine at TDC, on the compression stroke, and then checked the sprocket marks, roughly parallel to the head.
mxrose3
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mxrose3 12/23/2014 8:21pm
12/23/2014 8:21pm
some people will weld the cam gear in place to keep it from spinning:
ryanh827
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ryanh827 12/23/2014 11:05pm
12/23/2014 11:05pm
bought a new cam i did spin thanks for the replys
MotoX85
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MotoX85 12/26/2014 4:24am
12/26/2014 4:24am
MotoX85 wrote:
YES, almost guarantee that is your problem. Have had many 250s do this.
ryanh827 wrote:
just curious how did you figure out that was the problem
The very first one I put engine back together and spun it over by hand and the valves hit the piston. So at first I thought the timing was o ff. After triple checking the timing and thinking the gear had to of moved I called a friend who had a stock cam (he had bought an aftermarket) and put it together with that one the valves no longer hit and everything was in time. Ordered a new cam and problem was solved. Believe that was a 06 or 07 CRF250

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