WR426 Engine Rattle?

My '00 WR rattled too when it was new. The noise went away after about 50 miles. This was immediately after added a 45 PJ and 170 MJ and giving the bike an oil change. After changing the YZ timing, it rattled again for about 2 rides, again until the jetting was further dialed in.

If the noise is a high pitched, tin can (chink, chink, chink type sound) type sound, you may be a little lean. If it's more like shaking a paint can sound, I bet there's a loose bolt somewhere or it's just normal.

Also, before I rode the bike, I greased the bejesus out of everything in addition to tightening ALL bolts. There where a few engine mount bolts on the loose side as well as the header, tank, linkage, and carb boots.

Tighten everything down, I bet that will help.

The YZ/WR's do sound different than a typical 4 stroke.

As I said in an earlier post the bike is awesome! One thing though. What is that terible engine rattle at low RPM's? My buddy and I both bought one last week. We both have the rattle in the engine! Mine is twice as bad as his. We tried each others bikes and verified it wasn't the riding styles, but we both have the noise. Another friend just bought a WR426. He had a 00 WR400 prior to this (and yes HE is rich!), and he says the 400 didn't have that rattle. His new 426 does. I haven't ridden his, nor him mine, but I am concerned that this is or will be a problem! And why is mine so much worse? The dealer says he doesn't have any clue about the noise, but since the bikes only have a 30 day warentee, I need relief fast.



After first riding years ago on a XT500 and a TT500 and selling them, my sons have a dirt bike and a four-wheeler, I bought a WT400. After riding that and jumping on a friends YZ426, I bought one myself. Both his bike and my bike ping under low rpms, putting racing fuel in it made it worse. I also noticed that my head pipe was glowing cherry red towards dark. I changed the pilot jet from 42 to 45 and the main jet from 172 to 175. Have not rode much because of the snow but the pipe has not been glowing red. Starts better. Have checked TP voltage and seems okay. Hope it helps you.

I have a similar noise coming from the lower right side of the motor. A while back everyone had me freaked out about the Primary Gear key shearing and exploding. So I took my bike around and had people listen to it. Some thought I had this huge problem, others didn't think anything of it. Finally I stopped at this one Yamaha dealer and they had a 2000 426 in for service. We bumped it off and it made the exact same noise as mine. It was heavily raced but ran great. Mine is a trailbike and it runs also runs excellent. I figure tis is a natural noise that exists as my motor beds in.

I've tried different oils and it still makes the same sound. It's kind of a Bzzzzzzz like a chain but real light sounding. It is definitely from inside the right side of the motor. I think it's normal.

Roostn in Denver

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