Yzf400 / 440 ?

I tried a search, with no help....

My brother-in-law smoked the piston on his 1999 YZF400. Needless to say, he needs a replacement cylinder, or recoat the old one. We are thinking about making the displacement larger so he can beat a few more 450's. Most of the bigger bikes are behind him, but second or third place just isn't good enough for him. :excuseme:

I heard that it's possible to install a YZF426 cylinder on a 400 and make it a 440. Is this even possible? Any mods such as machining, spacer, etc? Any links to threads, web sites, or anything you can offer would be appreciated.

Powroll has an OEM parts list on their website to make the 400cc into a 426cc. They also have a 2mm stroker mod to turn the 426 into a 440cc. Upgrading to the 426 seems like the best bet price and reliability wise. If you want to get the cylinder redone check out US Chrome. Although it will probably be cheaper to just buy a new OEM YZ426 cylinder. The cheapest place for OEM parts is the Thumpertalk store or Generation MX. I believe the two are one in the same. Here are the links. :excuseme:





Thanks for the reply Speedracer. That Powroll web site helped a bunch. We can make the 400 a 426 with bolt-on parts, then could make the 426 a 440 by stroking. (As I understand it anyhow.) Money and time are tight, so we may stay 400, or at the most, go with the 426. Thanks again.

You could go to a 450 setup with a 400 using oem yamaha parts if I remember correctly. My local engine builder and I talked about going that way with my 400 when it was in need of new rod, cylinder replate and so forth. You would have to use an 06 crank with it, that is the only odd thing I remember about that route. For some reason only the new cranks would work for the conversion and of course you will need a 450 cylinder. The 450 route was going to cost another $350 to $450 more on top of the initial rebuild cost for the 400. There may be a few things that may have to be worked out in that conversion that I don't know about because we never attempted to do it. This is just something to throw out there for further review, it may just be what you are looking for.

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