Slipped Cam/Sprocket 99 yz400

7 replies to this topic
  • jasonknight

Posted January 08, 2012 - 04:32 PM


Hey People, not exactly sure what is going on here but I have a few theories. 6 months ago I reshimmed the valves and didn't time it right...result: intake valves kissed the cylinder:banghead:. I have since replaced all 3 intake valves and i'm making damn sure its right this time.

So this time I wanted to make dame sure the timing was right. I've done my research and have timed everything to the right marks on the cam sprockets and the crank. i also replaced the timing chain just to make sure everything was just right.

I put everything together but something still isn't right. I am able kick through the compression which used to be impossible without hitting the decomp lever. I've read though some other posts that had this same issue, but the problem has always been the timing. I know I have the timing correct as far as the marks go. I'm starting to suspect the sprocket slipped on the cam shaft when the valves hit piston. is that even possible? is the cam sprocket press fit on there?

this is my first time trying to post up pictures here, hopefully it worked, if not, more posts to follow until I get it right.

Thanks in advance for any help

  • jasonknight

Posted January 08, 2012 - 04:40 PM


Here are the pictures I took yesterday when we had it apart.


any thoughts?



Posted January 08, 2012 - 06:29 PM


According to this link it looks like you have it wrong.


  • DC_Excitement

Posted January 08, 2012 - 06:31 PM


yes, it is possible that the sprocket slipped on the cam. and it looks like your intake cam did slip. you need a new cam

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  • grayracer513

Posted January 08, 2012 - 07:52 PM


ignore the 13 pins thing when dealing with a 400; they're different. The the cams are timed correctly as to the sprockets (assuming that's at TDC, but the intake cam has definitely slipped in the sprocket. You could have this repaired, but at the end it would cost you more than just buying another cam. Good excuse to go with a new pair of Hot Cams with auto decomp, I'd say.

  • jasonknight

Posted January 09, 2012 - 08:41 AM


Thanks for chiming in gray, thats the response I was looking for. Gonna order it now.

  • jasonknight

Posted January 17, 2012 - 02:30 PM


just a quick update/closure post. got the new cam in and everything is running good. Timing it was still kind of sketchy, couldnt get all 3 timing marks (crank, intake cam, exhaust cam) to line up perfectly, but got them as close as possible. Started in a few kicks after not running for several months. Pretty stoked! Thanks for all your help.

  • grayracer513

Posted January 17, 2012 - 02:45 PM


The marks never line up perfectly.

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