06' wr250 engine in a 03' yz250 bike

Did a search, didn't find anything in faq to help much

buddy of mine is wondering if you can put a 06'wr motor in a 03' yz bike?

Got the yz without a motor, found a wr motor

Motor mount in?

How about wiring? Which cdi will work?



May need to do some welding or move some of the tabs on the bottom mounts. I think the swingarm bolt holes are different sizes too, so might have to bore the case hole mm or 2 so bolt will fit properly. You will need the 06 cdi and wiring for the wr I think. The cdi is different between the yz and wr, along with the wr wiring harness. I think there are some threads here on leaving off the battery. There could be some serious issues with oiling though. 03 yz uses a right side hard oil line to right side case cover, can't remember the other line with the internal filter. Study that one some. Might be you could use the 03 lines on the 06 motor. Good luck and post some pics if you can pull this swap off. I've done some swapping and sometimes it works out great. Being handy with a welder is a plus.

thanks, I was thinking that there probably was some pretty major changes between those years also.

Anybody else have thoughts? This worth it or not? I guess he says he prefers the wr tranny.


As far as the tranny swap, I think I haven't come up with the final gearing I like yet, I need a larger rear sprocket, like 52T or 53T. The jump to 3rd is a little wider than I like. I got spoiled being able to pull the front wheel up in 3rd easily with the YZ tranny, and sometimes its a little effort now with 51T.

I may be wrong, but I think you guys are confused with the fact the the 06WR has the aluminum frame. It does not, it has a steel frame. Im not 100% sure, but I believe the motor will fit in without a single issue since the steel frame didn't change.

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