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difficulty installing camshaft

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2010 CRF250R. I replaced the piston and I'm reinstalling the camshaft like I've done many times before. This time there isn't enought slack in the chain to slide the camshaft into position smoothly. The sprocket side bearing will not slide into position because the chain is too tight causing the camshaft to be cocked downward on the chain side. The tensioner is adjusted all the way loose and should allow the cam to slide into position. It just isn't happening. I'm wondering if I installed the wrong year gaskets (too thick?) Can't figure this one out. Your help is appreciated.

Edited by dehotom

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Could be that the chain popped off the bottom gear. You can check it out with a flashlight just look from the top into the engine with the camshaft removed.

Edited by fransn

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My guess is you have the cam chain guide, (black peice of removeable plastic) in upside down, therefore putting too much pressure on the cam chain! Check it out brother hope this helps!

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Thanks, but the tensioners are not touching the chain. I can slowly kick it over by holding the chain. It spins fine, no kinks or binding. It's attached to the sprocket and rotates fine. it seems like the base and head gaskets are too thick (just replaced piston) which would make the distance from the crank gear a bit farther from the crankshaft causing less slack but the part numbers are correct. I just don't get it.?????

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i dont think that would be the cause... my 06 crf250r had this same problem for a while, i just took the left cam bearing and slid it to the left which allowed the cam to go lower down into the hed.. then once i got the cam chain on the sproket i slid the bearing back into place

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i had this problem on my 07 to. i was having trouble getting the chain to stay on the lower gear. and when it would there wasnt enough slack for the cam to go into position. however one day after messing with it enough it just went into position. this was after a month of working on it and getting to frustrated and walking away from it.

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check that the valve shims are fully seated in the valve retainer.

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just had to do it again today.. 6 times!!!! well anyways what you got to do is slide the left bearing over to the left so the cam is at an angle... then you work the chain on from the intake side of the engine forward.. i found this is 100x easier to do for some reason. hope this helps

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2010 CRF250R. The tensioner is adjusted all the way loose and should allow the cam to slide into position.

Correct me if I am wrong, but I beleive the tensioner is not supposed to be installed until after the cam is in place. I did my top end last year and had no problems whatsoever(other than forgetting to install the cam chain guide into the bottom of the jug!)

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The tensioner can stay in the head as long you retract it. If you don't have the tool to retract it, the easiest way is to remove it all the way before you start the job.

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