valve adjustment?

10 replies to this topic
  • Gerry B

Posted April 11, 2005 - 05:59 PM


I have a 2000 YZ 426 and it runs perfect. It always starts on one kick and has more power than I'll ever use! What happens when the valves are out of adjustment? Does it make noise? I am getting loud valve clanking noises when the bike is idleing. It seems that the sound is louder from the top of the motor near the valves and head. I went over to a friends house that has a 2001 YZ 426 and his engine is way quieter. All you hear from my bike is valve noise or knocking noise from the head. Anybody here have a guess as to what it is? Thanks!

  • GixRider

Posted April 11, 2005 - 06:27 PM


Pull the cover and check them. I just did this last weekend on my 01 426. Intake valves were a little tight and the exhaust were in the middle of the spec. Pretty easy job. No noise from the top... the bottom on the other hand... clank clank clank.

  • cowboyona426

Posted April 11, 2005 - 09:14 PM


Usually valves being loose is a rattle sound, not a clank. How long have you owned the bike? I'm wondering if it's not the CB gear key that many of the 00's have had problems with. The valves are fairly easy to check, you just need to remove the tank/shrouds, pull the valve cover off, and measure the clearance according to the manual. Adjusting them is a bit more work.
I would take a hard look at the CB key though. Do a search, there is a ton of info here on this problem. Good luck.

  • RJB

Posted April 12, 2005 - 08:52 AM


Now I just wish I had the right 'feel' for the feeler guages. Never sure if it is just right, or to tight. Anybody got some tips here?

  • cowboyona426

Posted April 12, 2005 - 09:52 AM


If you have to force it in, it's too tight. If it slips right in, it's too loose. There should be just a little resistance when it's just right.

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  • mx426

Posted April 12, 2005 - 09:54 AM


I bought some gauges from yamaha that have max and min gaps on either end. With these you can use the go-no go method. If you can feel a little bit of drag with the min mearurement, and the max measurement won't go all of the way in, you know it's in the middle. I only adjust them when the big side slides in the gap or when I can't feel any resistance on the smaller side. As for your question, you don't want to force the feeler gauge in but you should feel some resistance. Try the next bigger size and see if it goes in without forcing it.

  • RJB

Posted April 13, 2005 - 09:07 AM


thanks for the tips guys, will bear this in mind on the next check

  • grayracer513

Posted April 13, 2005 - 09:12 AM


The '00 had one little quirk that can end up causing a noise. The balancer shaft drive gear is located with a key on that year, whereas the later models had splines. If the nut loosens, it can make quite a racket. If you find this, replace the key and re-tighten it.

  • Serenity Now

Posted May 26, 2005 - 10:54 AM


Does anyone know of a link to a "how to" adjust your valves pdf file or something like that? I don't have the service manual for my 426, but I do possess a decent amount of mechanical ability (I've rejetted carbs, rebuilt forks, etc) so I think I could adjust them myself if I had some guidance. Pictures would e helpful too.

  • grayracer513

Posted May 26, 2005 - 12:36 PM


Does anyone know of a link to a "how to" adjust your valves pdf file or something like that? Pictures would e helpful too.

How about....
This (it's a page for a 250F. Same procedure, but different exhaust clearance. Yours are: Intakes - .10 to .15 MM, exhausts - .20 to .25 MM)

...or This one for a 426?

  • Serenity Now

Posted May 26, 2005 - 05:28 PM


Perfect... much better than what I found when I was searching. :)

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