Timing Chain slipped 2009 YZ450 How screwed am I?

3 replies to this topic
  • opie

Posted March 18, 2011 - 06:16 PM


Put a top end in my bike and put it back together and tried to start it. Kicked down hard and motor kicked over but sounded weird and no compression. I pulled the valve cover off and the timing chain had slipped off of the exhaust cam and pulled the exhaust cam over to the left. After taking the cams out I see that the lobes had made some contact with the head to the side of the lifter buckets. :thumbsup: So my question is how screwed am I? Can the metal pieces be cleaned out and then am I good to go or do I need to take it to a machine shop for some clean up work. Or do I have to buy a new head? Thanks for any help!

Posted Image


  • grayracer513

Posted March 18, 2011 - 06:48 PM


This clearly happened because you failed to install the cam bearing locating half ring (#3 below) under at least the exhaust cam cap. The ring ensures the correct lateral alignment of the cam in the head and with the other cam, and keeps it from walking over to the left or right. You need to find it, because it may be laying in your magneto waiting to kill your engine or some part of it.

The damage can likely be cleaned up fairly easily, but you will want to be sure that the buckets move freely and the cam caps are not damaged.

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  • opie

Posted March 18, 2011 - 06:58 PM


Thanks Grayracer! Yeah I found the clip which must have slipped out when I installed the camshaft cap but luckily was right on top of the head. Is this something I can clean up myself or should I take it to a machine shop? If I can do it myself do you have any recommendations on how to clean it up properly? Man, I feel dumb considering I've done top ends in the past without issue and then have something stupid like this happen. Thanks again for your wealth of knowledge on this site!

  • grayracer513

Posted March 18, 2011 - 09:13 PM


From no more than I see in the pictures, it's difficult to tell. It looks like it should be just a matter of deburring and cleaning, but you should have someone take a look in person.

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