00 YZ426F Engine Noise!

my guess would be a bearing issue - cam bearing or other bearing. My friends 00 426 got louder and louder - did not seem to stop performance - just got louder and louder.....

I "discovered" the same thing...I had never started my WR426 without my helmet on (yes, it's true! Gotta set the example for the little guy to NEVER ride without a helmet...), and when I put hotcams in a month ago I started it in the garage to break in the cams. I shut it down right away thinking that maybe the cam chain tensioner wasn't extended all the way. It was. The guides all looked fine. The sprockets were new. The oil has always been clean. I put it back together and started it again. Still the same. Lots of rubbing, clicking and clacking...machine noises. I called the wife out to the garage, and she laughed her ass off. Said that it's always sounded like that, and so do all my friends YZs and WRs. So, I called my buds, held up the phone, and thay confirmed. Yup, our bikes sound like that too. Have since new.

Keep an eye on the oil filter, change oil often, and enjoy.

Pheww that makes me feel better. I have just come running up from the garage underneath our apartment building.. Like you I have always had the helment on and my YZ 450 is almost brand new so I was very disappointed to hear all that slapping, thumping and whacking coming from the engine. I thought I was paying for being a cheapster and putting in 20 50 oil so I changed that to Mobile 1. Still the noise... Bike runs great pipe glows red too...

Does it sound like a rolling and grinding sound? I've had bikes with main bearings shot sound like this. Get a stethescope and hold it to the lower end. You should be able to tell what the noises are. If in doubt take it to Yamaha and ask that a mechanic listen to it, they shouldn't charge you anything. I just bought an 99, it has a aluminum skid plate, and no noises whatsoever.

i think i might know what it might be. i am going throught troubled times rite now with my 426. so far i have broke 2 shift forks in a row (taking it to yamaha dealer to inspect wear tomorrow) and the last time i put it back together it was making that knocking noise. i just put it in the back of my mind and rode on. after my 2nd shift fork broke (3days ago) i tore it back apart. not because of the noise but because of my fork breaking. and when i got to the top end i saw that the valves were hitting the cylinder slightly. this is certinly what was causing the knocking noise from my motor. might be what it is on yours to. make shure your timing is right. take the gas tank off and the valve covers. its a tight fit getting the cover out of there but it will fit (you dont have to remove the whole motor) lign up the mark on the flywheel and make shure your timing is right with the cams. if its not that it your valves might need to be adjusted

I bought a used 00 426 and it came with a horrible knocking almost clanking noise when u ran it. 426's were notorious for wearing down the keys that go between the gears and the counterbalance so i took apart the engine and just as i suspected i took out one of the keys (i think it might have been the counter balance one) and was soo worn out it was rounded causing it too have tons of access play and causing it to knock..put a new one in and has never been quiter since.

On 2005-03-01 at 6:52 AM, rws said:


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.

My 2002 yzf 426 has same noise 

12 year old thread here....

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