400 to 426

5 replies to this topic
  • rockieman

Posted November 18, 2005 - 08:39 PM


After weighing my options to rebuild my 400, I decided to go with a new 426 cylinder and piston for my 99 400. After doing some research in previous posts, it appears that the 426 cylinder, rod and piston will work on my 400. I need to replace the crank and this is where my dilemma lies....will the 426 crank bolt on as well? Based on some other posts that I have found it appears that it will. I'm going to replace the head and the entire valve assy, plan to replace this with the 400 head.
Anyone see any problems with my plans? I would hate to buy all the pieces and have them not work. :applause:
Thanks for any advice

  • Brettv

Posted November 18, 2005 - 09:36 PM


no worries, it will all work

  • Gadsen

Posted November 18, 2005 - 09:45 PM


Wow, with all those new parts, whats involved in making it a 450? Just a thought.

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

Posted November 18, 2005 - 10:13 PM


If you get a 426 crank you will also have to buy the crank gear that drives the counter-balancer gear. The reason for this is that with the 426s Yamaha went with a splined gear as opposed to the Woodruff keyed gear of the 400s. The other option is to have the 400 crank rebuilt with a 426 rod (~$150 at Eric-Gorr.com) and then you can maintain the current gear. This is the route I took.

  • rockieman

Posted November 19, 2005 - 05:13 AM


Thanks for all the feedback...I may rebuild my crank for the 426 rod and save a few $$$.
Thanks again!

  • Oasis_Flame

Posted November 19, 2005 - 11:59 AM


I made my WR 400 a 426 about three years ago.
Wiseco makes a 95mm piston that will fit on a WR crank. I freshened up the head and bought a 01 426 cyl., Wiseco piston 13 to 1, same WR cams on WR timing. Put it together and wow does it make power. Now have over 2000 miles on motor with no problems. Good luck :applause:


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.