YZ400 cam timing

Hi All - new to this and thanks in advance for your help. I searched around a little, but did not see the exact answer I am looking for so here is my issue:


Performed a top end rebuild with new timing chain, hot cams exhaust cam with decompression, valve grind, new piston rings, etc. After reassembling and timing per the manual (and help from this forum), the bike will not start. Tried everything with no luck. Pulled the valve cover off to check timing and timing marks look as it should per manual and this forum. However, when looking at the lobes on the opposing side of the cam, the lobes are at 8 and 2 o'clock rather than to 10 and 2 which seems to be "normal". image1.JPGimage2.JPG It looks like the intake lobes are off by 90 degrees??


Is it possible that the timing gear slipped on the cam? I am perplexed...



The intake cam sprocket has slipped on the cam.  You'll need to replace the cam.  Was there any evidence that is seized in the head?

Grayracer - thanks for the reply! That is what I was afraid of. It is weird - there is no sign of the cam seizing. It turns freely in the journals when torqued down and there is no sign of scarring on the cam on the journals. I will get another cam - now I am worried about it seizing as well...


At least the mystery is solved - thanks again!

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