converting a 04yz450f to a wr help

2 replies to this topic
  • skoke70

Posted March 17, 2009 - 07:13 PM


OK, I have a 04yz450 that I have owed since 05, I love the bike but hated the 4 speed for the type of riding I do (tight woods and open roads). Last year I found a great deal on a complete 5 speed transmission out of a 04 wr450 so I had the swap done. It was liking having an all new bike with the wide ratio 5 speed, I love it! I got a 25 good rides on it before the used tranny went out on me. I think a rock slammed into my shift lever causing my shift forks to bend, next thing I know I was popping out of 3rd, 4th and 5th gear.
Well after a long search I found a gut with a complete motor out of a 03 wr450. apparently he tried to put in the wrong size spark plug and striped the hole. Instead of fixing it he found a great deal on an 04 wr and bought it keeping the 03 for spare parts.
I'm going to go and pick up the entire engine from him tomorrow. My plan was to put the top end off of my yz450f onto the wr engine. He also mentioned how he just replaces the starter on the engine which got me thinking, hum electric start and a head light? I knew I would have to have the wiring off of the 03 to make this happen so I called him to ask if he would part with it. Well he said the wiring is still attached to the frame and that I would also need the sub frame for the battery compartment an fuse box, for an extra 100$ I can have them both with the title. I could not pass it up for that price plus he throwing in the front headlight.
Here is my question to you all. Is there anything else besides the top end from my 04 yz engine the I should swap over (crank, piston?) Also how reliable are the electric starts on the 03? should I even bother doing it?

Thanks for the help

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  • grayracer513

Posted March 17, 2009 - 08:05 PM


If you want the WR electrical system, even if it's just for the lighting output, you will need the crank, and the crankcases, as well as the complete ignition/generator/cover assembly. You'll need to use the WR ignition as well, unless some rewiring of the stator is done. The entire top of your YZ will drop right onto it, though.

I think I have heard something about issues with the '03 e-starters, but you'd be better off asking that question in the WR forum.

  • L. Euler

Posted March 19, 2009 - 04:30 AM


I just did an 03-04 starter conversion on my 03 WR450. The 04 stater has a back torque limiter so that any backfire on starting will not be transmitted to the starter motor. You can find the details here:

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