YZ400-426-450f parts interchange

I just acquired a 99' YZ400f.I was wondering if the 426 or 450 cylinder would fit on the 400.And what other parts are interchangeable.The bike I have had the piston hit a valve.I haven't got it apart yet to see exactly what is wrong with it.But any help would be great.

No to all the questions. You probably will be better off getting parts from ebay or some on line OEM parts service like Yamaha of Troy. Best of luck.


I had the same problem with a 98 400 about the head hitting a valve, it came down to a faulty top-end job that the dealer fixed for free do to the faulty top-end. The valve fell into the cylinder thus hitting the piston

Thanks for the info.After looking into it more closely I found the 426 head and piston can be interchanged with the 400.It cost very little.I got a 426 head off e-bay for 120 and the piston/jug for 80.Im going to send the crank out to have it stroked by 2.5mm and make a 440 out of it.I talked to a bunch of people and that have had it done and they say the differance is incredable.

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