05 WR 450 Tranny

Ok here goes....will an 06 YZ450 close ratio tranny fit into an 05 WR450 motor. I want to make a close ratio, electric start YZ450 motocross bike. I already have:

2008 YZ450 frame and components(everything but motor)

2005 WR450 motor with DrD oil tank thingy removed

Complete WR450 electrical system

Blown up 2006 YZ450 lower end

My question is: Also, is the 06 WR 450 motor the same as the 05 WR motor?

thanks for the help..............

No, the trans won't fit.

The '03-'05 YZ450 and the '03-'06 WR450 are the same basic engine design. The biggest difference in the two is the left crankcase, generator assembly, including cover, and the crankshaft. The rest of the thing is pretty interchangeable.

The '06-'09 YZ450 and '07-'09 WR's are a different engine, with there being over 100 part number changes in the YZ engine alone. The thing that is hanging up your project here is that the '06 YZ trans assembly is 12mm wider overall than in the earlier models.

If you are determined enough, you can actually use a 426 trans, but it won't be a drop in, and I don't have the details of precisely what yopu would need to modify to make it work. I do know that a first generation 5 speed has been used in an '03 YZ450, and since you can interchange the complete trans from an '03-'06 WR into an '03-'05 YZ, I would assume it can be done. Sounds like an awful lot of work, though.

check out the YZ450 forum. there is a post in there about putting a wr transmission in to a yz. i'm assuming you can go the other way too :thumbsup:

i can't remember too many details about it, so give it a search and see if it's applicable for you.

The problems greyracer is referring to is not that you can't do it at all, it's that you can't do it across the different generations. The 06 YZFs are aluminium frame and have a completely revamped engine. The transmission will not fit into a steel framed WR with the earlier engine design.

The problems greyracer is referring to is not that you can't do it at all, it's that you can't do it across the different generations. The 06 YZFs are aluminium frame and have a completely revamped engine. The transmission will not fit into a steel framed WR with the earlier engine design.
Yeah, that's what I said. But if you'd like to put a close ratio 4 speed in your '03-'06 WR, it will drop right in place. :thumbsup:

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