04 WR450 lost 1/2 of it's power

Problem with my 04 WR450 (which has a 480 kit). Took the head off only to check the wear on the bore and piston (which was fine). On my 1st ride afterwards, went one mile rather slowly, and the bike lost about 60% of its power all of a sudden, sounds like its not hitting on all the power strokes. Been fooling with it in the shop, it will start up, but sounds like crap and won't idle below about 1/4 throttle. Took the valve cover and verified that the cams and chain are fine. The compression release works like it should. Plug is fine, tried another one. Spark is real strong.

Any ideas?

Edited by ertxc

Cam chain timing is off by one tooth.

Cam chain timing is off by one tooth.

what he said :smirk:

Interesting you said that. When I pulled the valve cover off I did notice that the intake cam was off by one tooth (was POSITIVE I did not put it together that way, how could it have slipped?) I retimed it, started it again, and it still runs like crap.

EDIT! (11/8) : Found the problem, the pilot jet fell out, was laying loose in the bowl. Sure didn't run good at all w/o a pilot.

Thanks for all the replys

Edited by ertxc
Found the problem,

I was positive too...

streched cam chain causing slip, bad chain tensioner, valves may need adjusted, carb probolems maybe??????????????????????

Edited by bakeyz426f

the cam sprocket can spin on the cam, usually due to the cam seizing in the head...

hope not, but have seen a few do that...

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