WR426 Big Bore Update

1 reply to this topic
  • jonova

Posted October 04, 2005 - 06:55 AM


I know some of you were curious how my big bore transformation went on my 01 WR426. Well the bottom line is that the bike absolutly rips. :banghead: I bored it to a 444, nikasilled the barrel and went with a wiseco piston. I put in a set of hot cams and had the head ported by Kenz Cycle Tech in AZ. I have nearly 1000 miles on the motor and it is still running strong.

I was concerned that with the cams and the head work the motor was going to be too hot for single tracks. I have done approx 300 miles of single track in Baja and have had no over heating problems and the bike actually behaves at low RPM's. But when the terrian opens up is when the motor is the best. It just keeps pulling. I drag raced two KTM 525's and a XR650 and pulled away from em. I am nothing but happy with my motor. :banghead:

The only issue I had was getting the jetting right. Some people say to put in bigger jets and others say put in smaller ones. The big ones make it too rich. So this is where I'm at now.

170 main
yz450 needle @#4
42 Pilont
1.5 Air Screw
the rest is stock

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Dan_Lorenze

Posted October 04, 2005 - 06:59 AM


Excellent!!!! I love to eat 525s and 650s..... You gotta love that 5 valve pullin and pullin away... Just when you think you're out it just keeps pullin.... Braaaaap.... :banghead:


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.