WR 426: Any advice for "mods"?

11 replies to this topic
  • OleFortThumper

Posted April 30, 2005 - 06:36 PM


I have a 02 WR 426 that is basically stock with the exception of some plastic and Acerbis Handguards. I am on a pretty tight budget but would like to add some worthwhile mods to my bike. :naughty: Does anyone have any cost efficient while effective suggestions?

  • Rattler88

Posted April 30, 2005 - 07:36 PM


No cost will be the throttle screw cut and the gray wire, also remove the air box lid.
The best mod will be replacing the exhaust cam with the 03 YZ450F
with autodecompression about $150.00 and remove the baffle if you
cannot afford a after market exhaust. :naughty:

  • sigepmock

Posted May 01, 2005 - 07:19 AM


I've got the same bike as you and agree with Rattler88, cut the grey wire(free), cut the throttle stop screw(free or only a couple $ for the YZ throttle stop), and get the YZ cam with the Auto decomp., it makes starting it almost as easy as a two stroke. If don't want to spend the money on the cam, at least rotate the stock exhaust cam to the YZ specs, this will give you a lot more throotle response and rev up top. Also get the ZipTy Racing air screw. It makes quick work of fine tuning the carb. for weather and altitude changes.


  • Hays82

Posted May 02, 2005 - 10:11 AM


Rattler, when you say 'autodecompression yz cam', does that mean I wont have to use that little lever every time I want to start, or did they do away w/ the decomp lever after 2001 ? If so, how hard is it to change out a cam (aka: how much will the shop charge me?)? Thanks a lot

  • Rattler88

Posted May 02, 2005 - 05:00 PM


Yes, that is the good news that the lever and cable now set on the old spare parts
bin and they went to the autodecompression cam in 03 if you use the YZ it does
a real nice job increasing low to mid range with any loss on top, also you will get a
lot quicker throttle responce.

  • 96warrior

Posted May 04, 2005 - 07:29 PM


So there isn't anything sepcial that needs to be done, to run this cam? My bike is an 01.

My Brother has an 01 wr250. We baisically do the same stuff to both bikes (tear down, and mod them together).

Would it be possible to run a yz250f cam in an 01 wr250f also?

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  • Rattler88

Posted May 04, 2005 - 08:58 PM


You will have to get the proper shims for your valve clearance
and on the 250 you will have to check thouse threads you
can get the info here http://www.photonrac.../PDF/450cam.pdf
for easy to fallow instructions. yes just checked on the 250
so you need to go here also http://www.thumperfa.../autodecomp.htm

  • byggd

Posted May 05, 2005 - 08:52 AM


Greetings All. I am thinking about doing the same mod and I'm just wondering. Why use the 03 YZ450 cam vs the 03 WR450 cam? I trail ride and want to keep my beast as tame as possible.

  • Rattler88

Posted May 05, 2005 - 11:55 AM


They changed the head on the 04/05, thats why you need the 03 and the cam is a little shorter over all on the 04/05, also the YZ cam really made a difference on the throttle responce witch is nice in the tight stuff and seems to help keep the bike from stalling.

  • byggd

Posted May 05, 2005 - 12:00 PM


Thanks Rattler. YZ cam it is then!

  • don319

Posted May 05, 2005 - 02:39 PM


I have an 02 WR426. Do the free mods in stages and see how you like the power changes. I did mine in the following order....Throttle stop, wire, airbox lid, GYTR endcap, Twin Air filter. Out of all the mods, the endcap by far is the biggest power improver. I didn't rejet. I put the wire back on and really liked the way it ran so left the wire on. This bike has lots of low grunt, still is quiet, and for wood and trails has more power than needed.

  • Vibeguy

Posted May 05, 2005 - 08:26 PM



If you remove all the manual decomp stuff after the cam mod be sure to install the TT decomp plug and do not use the $3 plug from Yamaha, it won't stay in. The TT decomp plug is physically retained by a screw and will never come out.


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