What are peoples experiences on WR400 -> 426 conversions

Hey guys,

I'm just working out what parts to buy for my WR400 as i have the engine split in half on my desk next to me.

I'm considering the 426 conversion. Now i don't need to know how to do it as its been covered a million times here. What i was wondering was what were peoples opinions of the conversion. How did it change the bike? did they have to rejet? what other supporting mods did you guys do and with what success.

I pretty much have to replace everything anyway, except for the cylinder. I'm just wondering whether or not its worth the stretch to buy the 426 cylinder when i don't really NEED it (mines got light scoring which apparently can be cleaned up with a brush hone).

Any help would be appreciated,


I own a 426 but i rode my uncle's wr400f and it was a solid bike... it had a very good bottom. Mine is a original wr426... not a convert, but i can tell you that my 426 has about the same bottom with WAY more on top and it revs MUCH faster and higher! I think this is due to the titanium valves. As far as i could tell, I guess that the 426 conversion would be a good move, but then again I'm on a true 426 with all the proper settings!

Also, how does a WR400 converted to 426 w/ hotcams compare to say, 06/07 WR450's for straight line performance.

My old man just got a new 07 WR450, just wondering how itd compare. His bike is pretty crazy though :applause:

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