250/426 valve shims

7 replies to this topic
  • Strattos

Posted December 11, 2007 - 12:23 AM


I've just pulled my 02 WR426 down following a gearbox failure and am going to adjust the valves while the motor's out.

Can I use the shims from a WR250 in my 426?

Also, two of of the inlet measurements are right on the minimum at 0.1mm, but one is 0.12mm

According to the manual, shims come in .05 increments.

Now this is not a problem in relation to the first two valves, but if I go up one shim size on the 0.12mm clearance, that will take me to 0.17.

The book gives between 0.1 and 0.15 as the recommended range. Do I leave the third valve or change it to 0.17?

  • byggd

Posted December 11, 2007 - 05:27 AM


Hot cams lists different kits for the 250 and the 426 so evidently not.:banghead:

  • GCannon

Posted December 11, 2007 - 09:08 AM


The shim diameters are different.

  • 1157mik

Posted December 11, 2007 - 02:01 PM



yes look at the shim kit`s offered by hotcams`, i`ve just ordered both cams - the 400/426/450 use 9mm shim`s and the little bro`s use the 7mm shimmy`s

i think - ooh- not done that in a while!!

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  • Strattos

Posted December 11, 2007 - 06:59 PM


Thanks guys. Cleared that up nicely. Cheers.

  • dominator426

Posted December 11, 2007 - 07:35 PM


Most of the original shims in your 426 are not in .05 increments. You should be able to switch most of them around to achieve close to middle of setting range on all 5 valves. If your third valve already has a .05 increment shim, leave it at .12 mm. (.10 -15 mm int./.20 -.25 mm exh.)

  • SXP

Posted December 12, 2007 - 11:21 PM


If you want shims in 0.01mm increments go to a Honda dealer and order shims for the CRF450. They are also cheaper than the Yamaha shims.

  • Strattos

Posted December 14, 2007 - 09:29 PM


Hmm thanks for the tip re the Honda shims, i'll do that.


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