99 WR400 and 2002 WR426 parts compatibility

Gidday Folks,

I have the chance of grabbing a 2002 426 real cheap but before i commit would like to know how compatible the parts are ?...

I'm guessing wheels, brake disc, callipers, seat, tank, radiators, frame are all pretty matched ?.. but how about engine parts ?... will a 426 head fit a 400 motor ?..

Any information would be greatly appreciated.

As far as the engine, the connecting rod (big end), primary drive gear, and piston are different, as is the cylinder (bore) and clitch (426 is better). Head will work but you have to drill the boss for the hot start port unless you want to use the (better) 426 carb with internal hot start. Fork valving is different (a bit better) on the 426. I remember reading once that either the swing arm pivot or the rear axle is a different diameter, but I'm not real sure on that. There is a bit of difference in the frames in that the 400 has the tab for the remote hot start. The lower mounting tab for the shrouds on the radiators is at a bit different angle so the shrouds are not quite interchangeable, but can be worked (or just use 426 radiators and shrouds together). For the most part, the 426 parts will supercede the 400 parts, though you may need to use them in "chunks" (for example, the 426 crank and primary drive gear; or the entire clutch; or, obviously, the piston and cylinder together). If it's cheap, it will give you plenty of spares!

Thanks Birdy426,

I was reading through various threads yesterday, after posting this one, and it seems that brake rotors and hub widths are different so the wheels aren't compatible either.... without some minor mods anyhow. I love my 400 and was hoping just to refresh it a little with some of the parts from the 426. I’m now thinking I might take the 426 on as a separate project and get back to it's former glory and keep the better bike... decision time !..

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