Wr 426 auto decomp: what size shims?

7 replies to this topic
  • Cpt_sarge

Posted March 08, 2014 - 12:52 AM


Hi guys,

I have some 2005 yfz450 cams for my 2002 wr426.

I understand the procedure & feel confident I can perform the cam swap.

When other people have swapped the yfz cams into their wr 426 what size shims did you use?

Please only answer if you used yfz cams in a wr426. I'm not using hot cams.

The reason I ask- I don't want to spend £50 ($75) on a shim kit. Ill order a range to suit as individually they are £2 each.

Many thanks

  • miweber929

Posted March 08, 2014 - 03:25 AM


That's not how it works, you have to measure after install, wear on each bike is different. Honestly, buy a kit, you'll use it eventually.


  • bg10459

Posted March 08, 2014 - 04:24 AM


Just measure and calculate the shims you'll need. There's a chance you will be able to use some of your existing shims. You're not going to need more than 5, anyway. Then order OEM Honda 450 shims. Most 450's use the same 9.48 diameter shim and Hondas come in smaller increments than Yamaha's.

  • Cpt_sarge

Posted March 08, 2014 - 10:57 AM


Okay thanks for the input gents.

To anyone who has done the auto decomp cam swap please can you tell me the replacement shim sizes you used.

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  • grayracer513

Posted March 10, 2014 - 11:19 AM


You're not getting it.  Every engine will have 5 different shims in it than any other one to start with.  Then, it's a matter of what the clearance is with the new exhaust cam (and that's another thing, you don't swap both cams in from a 450 because if you do that, you have to time them with a degree wheel.  Use only the exhaust cam.)


No one is going to be able to tell you what shim you will need.

  • Cpt_sarge

Posted March 10, 2014 - 01:10 PM


No, I am getting it.

I can make an educated guess on what shims I need from the feedback I receive. I can then use an assortment of sizes as necessary.

It is also possible to sand down a shim if you know what you're doing.

Please do not imply I don't understand. It is you who misses the point good sir.

  • grayracer513

Posted March 10, 2014 - 02:44 PM


If you know what you're doing, you would not attempt to sand down a shim, because it is impossible to do so uniformly or precisely parallel to the unsanded side. 


Carry on.

  • Thermos O flask

Posted March 12, 2014 - 02:47 AM


I just did a yz450 cam in a wr400- no shim change required ( lucky) and I had box of shims on hand. :)
Buy the box . I went through the " buying the shims I needed etc" then installed and they were still out if spec , eventually you spend the price of a box on individual shims.
Don't try to sand them... Herschel


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