00 YZ426F Engine Noise!

Ok... I've searched and read and searched some more then read some more. Here is my "issue":

My bike developed a "noise" coming from what I think is the engine. So I went investigating. I checked valve clearance. They were a little out so I went ahead and reshimmed. Put everything back together... started up... hmm... noise still there. [i'll describe noise in a moment]. So... I was concerned about piston/rod/crank problems. So... again... top end comes off... check out the lower parts [didn't split cases or anything]. Well everything appears to be fine. Parts seem to be fitting nicely, no clanking around or anything. No loose needle-bearings. So back together it went. When I got finished it was late and a bit dark in the garage. When I started the bike... much to my dismay... noise still there and then I saw it! The red-glowing exhaust pipe! Oh my goodness I nearly lost my mind... Luckily I jumped to the web and came a searching on TT. Found out that this is not that unusual to see the red glow in the dark... still a little concerned... but hey if others are seeing it... then ok for now. Still searching for the source of this darn noise. I pulled the water pump cover off and checked the impeller out. It's in one piece [which is always nice]. However when I manipulate it by hand... I can rotate it to a stop then get a "click" in which is moves a little more.

Well... it seems like the noise is not constant but it's prevelant. It sounds like a "grinding" kind of noise but nothing looks ground. It's loud and unnerving. I'm losing confidense in this little machine. I don't want to be out on a ride and get stranded, or worse be in the air and have it cut out! OUCH!

Anyway... any and all suggestions would be appreciated. I'm continuing to search the forums as well as the bike itself. By the way... this noise is present sitting on the stand whether idling or reving.

If it really is a grinding noise then it should show up in the oil.

On the street bike, I just try and fit the ear plugs in tighter.

In general if it runs fine, and there's nothing explicitly obviously wrong then, it's probably not a big deal or even more likely it's all in your head.

My $0.02, FWIW.

Did you check the timing chain rubber and chain tensioner for wear ?


That's what I thought... oil is clean as the day I put it in there... filter clean as a whistle. I describe it as a "grinding" noise but it could also be something like a "knocking". It's definately not a "squeeling" sound. I read that the "knocking" could be from low octane. So... I am trying some octane boost and new fuel to see if that might help resolve.

I thought that it might all be in my head [or ears]... However there are others [my riding buddy and my wife] who listen to it and they say "that sounds horrible". Granted neither are mechanics.

At this point... it's definately in my head... the bike rides fine. No loss of power, starts fine, oil is clean. All indications say things are fine. Except that darn noise. It's got me phyched out! I am of the mind to just ride until whatever it is just lets loose completely. Then at least I'll know what it was.

Definately not the preferred method of troubleshooting :)

Thanks for the feedback.


Actually I looked at the timing chain and I didn't see any visual signs of deterioration. The tension "feels" fine when the tensioner is in place. The cam gears and crank-shaft gear teeth all look good. One thing that I don't know is what a new timing-chain guide looks like. It could be that they are worn down allowing the chain to move more than normal.

Hmm... I'll have to see if I can get my hands on a couple new timing-chain guides. Thanks for the suggestion.

Did you check the counterbalancer key? Some of the 00 model bikes had issues with the CB key getting loose and shearing. Do a search on here and I'm sure you'll find a ton of info on it.

Start the bike up and while its running put your hand on the clutch cover, If its like mine the noise goes away as soon as i put my hand on the cover. I think its just engine noise and the Mag cover intensifies it.

my bike has sounded like a yanmar single since new? still runs the same (if not better) noise is the same,same looking oil. if it ain't broke don't fix it! :)


Actually I'd read that a while back and that's something I just checked. I didn't find any pieces of a key or anything that looked broken. However I didn't have a flywheel puller so I never did take it off to offically set eyes on it. However.... this is on the list of things to do. Thanks!


The noise is definatly more pronounced on the right side which is why I started looking into the waterpump area. I've actuated the clutch [thinking that it might be related] but no change. I'm going to go home after work and give your suggestion a try. If all I'm hearing is amplified "normal" noise... I'll be one happy rider! Thanks for the suggestion... now come on 4 o'clock!


I hear ya mountainman... I don't want to be rooting around in there if something isn't broken otherwise... undoubtedly... I'll wind up breaking something. Actually... I've managed to strip the bolt that holds the decompression rod in the valve cover. This can be resolved with the auto-decomp cam mod... but for now... need to get this noise out of my head.

Thanks for the input... I'm about to set out and just ride if I can't find anything... just hope it holds together.

Ya Robert its kinda funny , when i first got my bike , used , i didnt hear anything abnormal because im a converted 2smoker and everything sounded different. As i got comfortable with the noises i dont know i just started hearing things . I noticed SOMETHING weird but couldnt put my finger on it. Then i started feeling around while the bike was running and feeling for vibrations, and when i put my palm on the clutch cover the noise went away, telling me that the thin cover , and possibly just the shape or just how close it acctually is to the clutch and components is amplifying internal noises. Check it out . Let us all know . :)

An aluminum skid plate will amplify the noise also.

CB gear key.

Dont even bother trying to replace it by making your own unless you have something that can sand perfectly even.


Actually I'd read that a while back and that's something I just checked. I didn't find any pieces of a key or anything that looked broken. However I didn't have a flywheel puller so I never did take it off to offically set eyes on it. However.... this is on the list of things to do. Thanks!

No need to pull it, just feel for excessive play. If there is a lot of play then its time to pull.

I have a 2000 426 also and although Ive never had a problem this is the one area that has always concerned me.

while out in glamis over presidents, i had problems with my bike. on the way back from olds it started to make a really loud noise. my buddy could hear it while riding in front of me. it sounded like it was coming from the water pump and i was pretty close to camp so i figured id just head back. well, i didnt make it. my bike locked up just a few minutes after i heard the noise. when i finally got home and got started on pullin her apart i noticed something funny at the bottom of my clutch after i pulled the clutch cover. so i pulled the side cover off and what do i find, six fingers broke off my clutch basket. after i got the basket out, i found that it was cracked in half as well. if only i woulda shut it off when i first heard the noise and got pulled back to camp, i would be saving my myself all the trouble of having to pull the engine apart again to clean everything. maybe you should just take it to your local yamaha dealer if you cant figure it out.

My old 00-426 made all that noise and more. It sounded like that new until the day I sold it. The more I listened to it the louder it got.

Now that I think about it as lJ said, I really noticed it more after I installed the skid plate.


Your experience is exactly the situation I'm hoping to avoid. I have reserve duty this weekend but when I return home, I'm going to pull the clutch cover off and do a thorough inspection. Sorry about your experience... but thank you for sharing so that I [and others] may avoid a similar demise.

I appreciate your feedback... thanks and good luck putting the pieces back together.


I'm wondering if it's just a matter of getting used to the noise for me... hmmm? I can "tune out" noise, heck I have 8 children at home! I just want to make sure that I've investigated all angles so I don't wind up stranded somewhere.

As for the skidplate... mine is currently of [kept dropping bolts and the plate was a great bolt catch, but couldn't get them back too easily :) ]. The "noise" seems to be more prevelent from the water-pump / clutch side.

Thanks for the input... I'm gaining a little more confidence in the bike being that I'm not the "Lone Ranger" in this situation.


While I had the cover off... I tried to manipulate [in numerous directions] the assembly. Didn't feel like anything was loose or out of whack... I'm going to keep an eye on this for a while to make sure things stay put.

Thanks for the help!

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