Yz450f to Wr450f - The right way!

So ive decided to turn my yz450f into a super moto/dual purpose. I redid all the cosmetics/bearings/suspension last winter so the bike is brand new. but it started knocking the end of the summer. all the top end is good so I gotta dig deeper so I'm doing a full rebuild.

Basically what I'm wondering is what I have picked out to replace will suffice for a conversion to WR.

here's a list of things I have picked out:

WR450f bottom end rebuild kit

YZ450f top end rebuild kit

WR450f stator/flywheel/stator cover

I have a number of questions I'm seeking answers to and wondering if anyone can help.

1. will the bearings and seals that come with the bottom end rebuild kit work with the YZF case.

2. Do I need anything else to make it work.

3. What gear ratio should I go with for 1st and 5th. I want to make both a little wider. 5th more than 1st. so its nicer on trails and on the highway.

4. how will changing the gear ratio of first affect second? should I just leave it be and go with just the WR flywheel and a wider 5th for the highway?

5. Any part supliers that you would recommend for the stuff I am gonna need? keeping in mind I live in newfoundland Canada.

I appreciate any help you guys can give me!

If you are talking about an '06-'09, You actually can convert to a WR450 electrical system... for about $1200:




If you have an '03-'05, you'll need a pair of crank cases to go with the same pile of parts as above. 


The gearbox isn't a problem (other than the expense).

There is NO reliable, practical way to add on-board lighting support from the stator; they're just too small to make that much electricity and be dependable at the same time.  



Just put a WRatio gear set kit in a YZ, and use Battery powered LED lighting.


If you want estart, it's much easier to just convert a WR.

so will all the bearings for the WR bottom end fit a YZ bottom end? I may just change 5th to the WR ratio. I'm doing it over the winter so I have some time to decide but ill be ordering the rebuild kit soon so I can start swapping out bearings because I have a crank bearing that's almost toast.

I'm going with a the WR crank and it comes with the rebuild kit but I wont buy the full kit if the bearings aren't gonna fit.

You still haven't said what year your engine is, but all of the bearings should interchange within the same engine family years. 


If you only use the WR 5th, you're not going to like the ratio gap between your 4th and the new 5th at all.  Furthermore, if you have a Gen1 YZ450 ('03-'05), you have no option but to use the complete transmission, including the shift cam and the forks.

my apologies. it is a 2008. and I kinda expected that. but it would only be for highway really. I'm not that aggressive that I would even get to 5th on a trail or track.. I was gonna change first too. but if I'm gonna do that its just as well to do the whole tranny because I think if I make first a little wider second is gonna be really short. so ill be good with

WR bottom end rebuild kit

YZ top end rebuild kit

new timing chain/tensioner (just because)

WR stator/flywheel/stator cover (w/freeze plug)

Should I go with the new CDI and wiring harness?

Heres my baby. She'll be a sexy dual purpose


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