Help 02 wr426 - Bad engine noise -t/chain,bearing?

Last Saturday had good riding day. When I got back start bike to drive off trailer and wash. The engine made a bad grinding chain rattle. Bike seem to run fine. I have check the following but noise is still there

Cams,Cam timing and chain,tensioner,oil change normal.valve clearance ok clutch looks ok. Noise is hard to tell were its coming from Very slight at idle get a little gas and there it is.

best describe as rattle grinding noise related to rpm. pulling in clutch does not change it. Bike is 7 month old oil change every 3rd ride well maintain. Any Ideas.

Please help. Bike starts and idles fine

Your skid plate bolts may have loosened causing it to rattle at certain RPM's...It happened to a WR owner on this site before.

all skid plates and guards removed - help its almost the weekend

Could your compression release cable be too tight or binded?

My '99 did something similar a month ago. The main crank bearing had apparently disintegrated. I maintain my bike just like you do. The crankshaft is being rebuilt as I write this. This is the second time it has happened. :)

Don't run the motor until you figure out exactly what is wrong. You could do more damage and it could cost more money if you do. All it takes is about a minute for metal shavings to destroy the oil pump and crankcases.

There is a keyed gear on the earlier bikes - my '99 - that the key wears out and lets the gear rattle. I can't remember the name of the gear & I don't have my manual handy. Do a search on my user name for a post around April of '01 - there's lots of info on the problem & fix.

I hate getting old.... 33 is gonna be a bitch:)


I had the same symptoms that you are having and it turned out to be a worn out cam chain. It was rubbing the inside of the hole that it goes through and producing lots of tiny aluminum shavings. Luckily, I caught it before it did any real damage. Good luck.

could it be a muffler bearing?

Search the YZ forum for counter balance gear noise. Early YZs had a problem with lose keys in that gear. Can be destructive if not fixed quickly.

thanks for the help

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