motor noise HELP

[Joenewb]

I have a 2000 YZ426F. had the valves shimmed a couple months ago when I bought it and it has been running great. Still does run great and start easily, but I'm starting to hear motor noise. its a tapping sound that almost sounds like the skid plate is loose but Ive checked everything and nothing is loose. The sound speeds up with rpm's and sounds tobe coming from the middle to top of the motor. I've taken the valve cover off and checked the bolts that hold the cams and theyre snug. the gears and chain looked good as well I couldn't see anything unusual. Any suggestions what to look for? I'm not going to ride it again till this is fixed.

[Gerry B]

The problem is most likely the woodruff key on the timing gear has gone bad. Its on the clutch side of the motor and its the small gear thats connected to the crank. In 2000, the YZ426 used a woodruff key on that gear. In 2001 and later, they swicthed to splines because of that failure in 2000. Its pretty easy to fix and its not expensive. It was a very common problem with the 2000YZ426. I had the same issue with mine. I had the same noises as you are talking about.

[ronbuell]

You sure its not a heat shield on the header or a loose muffler mount or head stay mount or bolt on the tank??

[grayracer513]

The problem is most likely the woodruff key on the timing gear has gone bad. Its on the clutch side of the motor and its the small gear thats connected to the crank. In 2000, the YZ426 used a woodruff key on that gear. In 2001 and later, they swicthed to splines because of that failure in 2000. Its pretty easy to fix and its not expensive. It was a very common problem with the 2000YZ426. I had the same issue with mine. I had the same noises as you are talking about.

If you let it go too long, it does get to be expensive, though. Needs to be checked.

[Joenewb]

How do I get to it? I'm a newb

[Joenewb]

You sure its not a heat shield on the header or a loose muffler mount or head stay mount or bolt on the tank??

Yes, checked all that. Nothing loose and coming from motor.

[grayracer513]

How do I get to it? I'm a newb

It's located under the primary drive gear, under the right side crankcase cover.

Manual:

http://www.yamahaownershandbook.com.au/?r=0

[Joenewb]

Thanks Grayracer.

I have the owners manual but still can't find the half moon shaped "key" in any diagram. What do I have to take off to get to it? Do I have to remove the clutch cover and the larger cover that it's attached to?

[Joenewb]

I asked a friend who is very knowledgable about bikes and he said it wouldn't run if it was the woodruff key on the timin chain.

[grayracer513]

Your friend is wrong, and you misread which part it is.

It would run if it had a LOOSE Woodruff key on the timing gear. (but not if it were sheared. However, there is no key of any kind on any of the timing gears in a YZF, which is probably why you can't find one.

The key is a square key, not a Woodruff, and it is located under the primary drive gear (do I hear an echo?). It anchors the balancer shaft drive gear to the crank. (# 9 in the illustration) The drive gear gets loose, and the key gets beat loose in the groove. If you let it go, it eventually distorts the key groove to the point where it isn't useable.

[Mxdubya_tee]

I think mine is doing the same thing and heard the same advice. So I'm going to attempt to change out the pin. However, I don't know which side of the engine to open up! I'm guessing it's the right side??? Right above the foot brake lever???

[Mxdubya_tee]

Hey Grayracer, I replaced the woodruff key in mine yesterday and thE noise stopped. However, now when I'm in gear and gas it, it has a delay in rpm. Like it's bogging out or something. Any idea why? Thanks.