02 valve adj settings ???


8 replies to this topic
  • SRE7

Posted September 21, 2005 - 07:41 AM

#1

Greetings All,

Please forgive me if this is not the place to post this question...I am pretty new.

I have an 02 YZ426 and my official owners' service manual states the valve clearance on the intake should be 0.10-0.15 mm...ok no problem!!

Well the Clymers (M491-2) manual for this same bike states on page 78 the intake should be set at 0.15-0.20....ok now a problem!!

Could I get some opinions on which is correct and what you guys have used??

Thanks for any and all help...

Steve

  • grayracer513

Posted September 21, 2005 - 07:56 AM

#2

Use the Yamaha manual.

The correct clearances are in fact .10-.15mm intake, .20-.25mm exhaust.

  • SRE7

Posted September 21, 2005 - 08:36 AM

#3

Thank you Sir....

I have noticed that your posts are quite informative and free of wasted, un-needed words. Your posts and comments are quite valued and carry authority....Thank you for all your help and insight...it is and has been a great service to many.

May you find a resource for your unknow interests that is as good as the "resouce" we have found for ours....

Steve

  • Yak

Posted September 21, 2005 - 09:00 AM

#4

Keep in mind that an american set of feelers which go in thousands of an inch are really too large for deciphering a .05mm change. Some of the measurement is going to be feel.

Also, keep in mind that the new shims come in .05 incriments, which is the total value of the spec range. So the valves really have to be fully out of spec before a change is needed. If they are in spec like .21 on the exhaust side, which is the tight side of the spec, then upping a size on the shim will throw it out of spec on the loose side to .26

General consensus is that its better to be in spec on the loose side, as valves tighten over time. So if you have a .20 exhaust measurement, you are better off going to the .25 spec.

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  • grayracer513

Posted September 21, 2005 - 04:26 PM

#5

Keep in mind that an american set of feelers which go in thousands of an inch are really too large for deciphering a .05mm change. Some of the measurement is going to be feel.

Also, keep in mind that the new shims come in .05 incriments, which is the total value of the spec range. So the valves really have to be fully out of spec before a change is needed. If they are in spec like .21 on the exhaust side, which is the tight side of the spec, then upping a size on the shim will throw it out of spec on the loose side to .26

General consensus is that its better to be in spec on the loose side, as valves tighten over time. So if you have a .20 exhaust measurement, you are better off going to the .25 spec.

I have to disagree. First, I don't own a set of metric guages, and unless I happen across one by chance, I don't plan to spend any more time trying to find one. The specs for your 426, .10-.15, and .20-.25, are equal to .0039", .0059", .0079", and .0098" respectively. .004, .006, .008, and .010 are so close as to be exact replacements for the purpose, and as a 30+ year pro mechanic, I will guarantee that you can't tell the difference between a .010" and a .25mm guage under the same valve no matter how good you are, if the guages are even made to that kind of tolerance in the first place.

It's true that service shims come in .05mm (.002") increments. But there are very commonly shims in the engine from the factory in .01mm increments, and you can shuffle these around sometimes to get precisely the clearance you want. Pro mechanics will have these in their personal stash from having done adjustments on customer bikes. I have also heard that Honda shims for a CRF450 interchange, and are available in smaller increments, but I haven't had a chance to check that.

If that is the general concensus, then I'm surprised to hear it. It is better from both a wear and performance perspective to have the valves at the tight edge of the specified range, and as long as the valves are in their prime and wearing slowly as they normally do, there's no reason not to try to keep them there. That's how they are set from the factory.

  • MNellis

Posted September 21, 2005 - 05:11 PM

#6

I..... I have also heard that Honda shims for a CRF450 interchange, and are available in smaller increments, but I haven't had a chance to check that.


I recently couldn't get the shims I needed from Yamaha so I used Honda shims and they worked fine. They too, however, only come in .05 increments. Or, at least thats what the Honda dealer told me.

  • grayracer513

Posted September 21, 2005 - 05:44 PM

#7

They too, however, only come in .05 increments. Or, at least thats what the Honda dealer told me.

Rats!
O..O
=o=

  • MNellis

Posted September 21, 2005 - 08:42 PM

#8

However, another option is to take a hint from my roadracing buddies who own Ducati's. The "lap them" with 400 grit emery paper to shave a thou or two. It can be a little work but they (the Ducati tuners) say it's necessary on the Duc's with those Desmo valves.

I'll bet if you took an old spring retainer it would make holding the shim easy and you could just sand away.

Might be worth a try if one is real anal about exact valve clearances.

  • grayracer513

Posted September 21, 2005 - 10:06 PM

#9

I'm probably going to be accused of being anal myself, but I would hestitate to lap shims for the simple reason that there's not a good way to assure that the surfaces are dead flat and parallel. In a desmo Duc, I'd be less worried about the closers than the openers, but even so....





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