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rockieman

400 to 426

6 posts in this topic

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

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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.

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

Thanks again!

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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:

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