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Yamahondaha

Who knows what won't fit a 99 WR400F Engine

9 posts in this topic

I wanted to put a 426 motor in my 99 WR400.

The rod end bearing at the crank pin failed and I hear the 426 is the most reliable of the WR's.

My 400 is California plated so I really want to keep it but I don't want to rebuild it only to have it fail again...

Do you know if I can bolt the 426 motor into my 400 frame?

I don't know if the outside dimensions of the motors are the same or not, I heard that the 450 motor requires a few adaptations to make it work and maybe the electric start would make that worth my time and effort.

I would like to hear from those who know what will interchange with the 400 and what won't. :applause:

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i think a 426 is a bolt in mod for the 400. but im not 100% sure...

I would think so by the look of the two but I am not sure if the 426 top end is longer or wider than the 400. If it is longer it might need a 426 motor mount...

:applause:

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im pretty sure that the outside measurements are all the exact same, its just internal parts that are different.

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im pretty sure that the outside measurements are all the exact same, its just internal parts that are different.

I just don't want to buy a 426 motor and find out I have to "rig" it to work.

:applause:

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I'm pretty sure the motor is the same externally but you might want to post in the Supermoto forum. I'm sure one of those guys has done the swap.

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I found out that the 426 motor will bolt into a 400 frame and you can also swap out the crank, piston and cylinder and have a 426 displacement

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I found out that the 426 motor will bolt into a 400 frame and you can also swap out the crank, piston and cylinder and have a 426 displacement

this is what I did..... I kept my 400 motor but replaced the crank, cylinder, piston from the 426. I also had to replace the head ...which I did ...with a 400 head.

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unless you've totally stuffed the bottom end there is no need to get another motor, just do what rockieman did and convert to 426.

here is a site you can compare part numbers to ensure that it's all the same

http://www.yamaha-motor.com/star/myyamaha/prompt/L3N0YXIvcGFydHMvaG9tZS5hc3B4/Parts%20Catalog/starthere.aspx

and here is a site where you can get genuine yamaha parts at around half the price your local yamaha thief, i mean dealer can supply them to you.

http://www.jp-parts.com/index.html

i'm in the process of doing the same so if you finish first let me know the hard bits.

good luck

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