wr / yz motor cases

12 replies to this topic
  • tweav

Posted October 23, 2008 - 04:03 AM


I've got a 07 wr450 and I want to build a spare motor for it . I know where I can get a 06 yz450 motor with no head on it . I know all the gears in the tranny are differant and the left side of the crank shaft , stator and stator cover is also differant . but I was looking at a parts book and noticed that the wr and the yz have differant main case part #s . Does anybody know what is differant at the main case ? can I use a Yz one?

  • doctorchopper

Posted October 23, 2008 - 02:22 PM


might have something to do with the starter mounts and drive gears

  • tweav

Posted October 23, 2008 - 07:13 PM


I"m sure I can put a wr tranny in the yz case in fact all of the internal parts are the same less the gears themselves . the clutch ,all the parts are the same less the lever that the cable hooks to . the crank is the same other then the flywheel side end. but the all of the cases have differant numbers all 5 parts of it. I understand why the stator/starter case is differant but after that I don't know

  • matt4x4

Posted October 24, 2008 - 04:21 AM


From my experience over the years, it seems YZ and WR parts are identified differently ALL the time - whether the part is identical or not, this makes it more difficult to know when parts are actually different.
I think in your case (no pun intended) the cases are the same, I cannot see a difference on the microfiche. There is nothing cast differently to accept the starter motor/clutch assembly.
Might want to go to a dealer and compare a new 08 wr450 and yz450 on the showroom floor.

  • grayracer513

Posted October 24, 2008 - 05:56 AM


In the case of the '06+ YZ and the '07+ WR450's, I don't know what exactly the difference is. But the YZ cases do have the starter mounting bosses, the boss for the WR clutch cable anchor, the pocket for the starter idler gear shaft, and everything else I can think of immediately. Someone who may be able to give you some insights would be the people at Zip Ty Racing. I believe the "WR" they campaigned was a hybrid.

As far as the trans goes, the output shaft, shift forks and cam are identical in both boxes. All the ratio pairs are different.

  • tweav

Posted October 24, 2008 - 03:33 PM


I 'm going to have the guy with the other motor take some good close up picks of it . so I can see if I can see anything differant .The weird thing I can't understand is why the two outside covers on the clutch side would have differant part #'s because everything inside on that side seem to match up ???????? Any clues ? I really hate to sound lazy but I don't really want to kick start my bike. I am wondering if there may be something machined differantly at the left main case to allow for the electric starter drive.

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  • grayracer513

Posted October 24, 2008 - 08:25 PM


I've never seen them side by side, but I know the YZ cases have at least the starter mount bosses and the idler pin socket machined into them.

  • tweav

Posted October 24, 2008 - 08:38 PM


So you guy's think it will work ?

  • grayracer513

Posted October 25, 2008 - 07:57 AM


Try dropping a PM to member gdbarr1976. He just completed a conversion to his YZ to use the WR magneto/generator, which necessitated using the WR left crank axle. He may have some more insight.

I can only go as far as to say that it looks like it will work.

  • tweav

Posted October 25, 2008 - 08:32 AM


I guess I'll just buy the motor ,and in the worst case . I'll just sell a rebuilt yz motor.

  • grayracer513

Posted October 25, 2008 - 05:25 PM


I'd be interested to hear what you find out.

  • tweav

Posted October 25, 2008 - 08:16 PM


As it turns out the guy has a yfz not a yzf motor. so I don't think it will work at all. it has an external oil tank. I'll keep looking

  • grayracer513

Posted October 26, 2008 - 07:06 AM


The hard points on a YFZ are different, too. It's more similar to the '05 WR engine, but it would not fit one of those, either.


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