3rd gear noise

During my practice session this Saturday I developed a noise only when I am in third gear on my 2000 426. Its sounds quite a bit louder than your normal chain slap. It is coming from what sounds like the the front sprocket on decel only. It appeared out of nowhere. I removed the plastic cover that protects the front sprocket thinking the chain was rubbing on it . No luck still there, I adjusted the chain to the proper spec, and still had the noise. The thing that is baffeling me is that when i was test riding it it would be fine for a few corners (no noise) then the rattle would appear, I would then stop look and feel to see if the front sprocket or chain was loose and would then start again and it would be fine for a couple more turns, and then the sound would be back. I am getting the sound only in 3rd gear, it makes no noise in any of the other gears. If anyone has any ideas or answers please help. Thanks John

[ April 07, 2002: Message edited by: YZFcrash ]

I just replaced a couple of tranny gears that were broken in my KTM 200mxc a few months ago. I started noticing a sound that felt like my chain was slapping or a rock was stuck somewhere near a sprocket etc... or a strong knocking sound like my rod was getting ready to let go. This happened during practice before a hairscramble race. I went ahead and raced the bike that day, and noticed that I was hearing the sound mostly only in 1st and 2nd gear and mostly when coming off the throttle. I tried to figure it out again after I got home and got the bike cleaned up. I put the bike on a stand and ran the motor through the gears while running. It seemed like the chain was kinked and it was kind of jumping once each revolution of the sprocket. I adjusted the chain, and took it to the dealer to see if he could figure it out and he was stumped. Make a long story short, I tore down the motor and found 3 gears in the tranny that had peices missing, thus the problem. Ordered new gears put it all back together and everything was all better. Hope this helps, it kind of sounds like it could be the same thing.

Even though this noise appears in 3rd gear, the '00 has a design flaw with the counter balancer key. It might be possible that you only hear this noise in 3rd gear. The quick fix is to install a new key stock. Even if this is not the source of your problem, you eliminate this potential problem before moving on to a potentially more serious issue.

I have had probs with 5th gear. This is a known weakness of the YZ426F when using it as the street-legal version for enduro-riding. The claws of the 3rd gear fall into the 5th gear and they seem to wear of easily when revving it out in 5th gear in heavy terrain. I tore mine apart(2nd time)and primary gears 3rd, 4th and 5th, and secundairy 3rd neede to be replaced, also the 1st shiftfork showed severe wear and tear, also replaced.

Yamaha did manufacture modified gears for the YZ426F, but they do not seem to hold out better?

If you don't trust your engine, tear it apart before it blows up on you.

Best Regards,


I lost dog teeth on 3rd and 5th gears . 3rd slides into 5th when shifting. $1000 repair . three months later back of clutch basket blew into three pieces. Lost faith in the bike and traded it!!

[ April 12, 2002: Message edited by: dan Rekito ]

[ April 08, 2002: Message edited by: YZFcrash ]


I have read a lot about the cb key problem, but everybody seems to say they hear the sound from the right side. My sound is occuring on the left side at the sprocket. Just wondering if this CB key problem wouldn't make any noise on the right side, but make noise only on the left?

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