wr426 engine in a yzf250 '04 frame

Will a wr426 engine fit into a yzf250 '04 frame without modifications to it, or will the engine mount need to be welded on a different place???


Do a test-fit and report back.

I think the holes in the frame are the same...at least as near as I can measure on my 426 and my son's '02 250...however, you will need the 426 engine mount plates. You will have to cut the coil mount tabs off of the 250 frame if they are still there (for head clearance), and you will have to find a place to mount the 426 coil...a solution to that may be to run the 250 coil as 04 was "coil on cap". If you don't have the coil, an R1 will work...search on here and you will find lots of info on how to do that. Swing arm carries a different P/N, but the swing arm bolts are the same diameter (bearings are different) so that shouldn't be an issue. I have an 03 swing arm on my 01 426. You will also have to use a 450 air boot as the 03 and up air boxes are different than the 02 and older, and the 250 and 450 use different size carbs. If you try this, let us know how it works. Another thought...The 250 suspension is even softer than the 426, though the quality of the damping is better. If you haven't had the 426 forks revalved for your style, you may want to consider popping for new springs for the 250 forks. The 426 shock spring should work fine on the 250 shock, but the 250 shock has better valving...

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