Splitting the cases

My 04 yz 450 with a ton of hours on it is making a bad noise in the trans area. I checked the timing chain; its ok. I also checked the clutch side: no problems there either. No metal in the oil.

What special tools do need to take it apart? The manual shows a puller to split the cases. Any other tips?

Thanks :doh:


I split my 08 yz450 and I didn't need any special tools. You can leave the crank assem attached to the left case half and pull the right side off the crank and trans. A manual should show everything you'll need to know. Also, an impact gun makes it nice removing nuts on balancer, crank and clutch.

Thanks tmoney, I should have the motor out of the frame today.

Fourth gear would seem to be the problem.


That is the 3rd pinion, not 4th. It is the gear that moves over and locks 4th in, but it's 3rd. 4th isn't visible in the picture.

Thanks for setting me straight, Gray. Is this normal wear and tear? I'm considering the wr450 5-speed swap. But the bike is only used for mx.:crazy:

No, not "normal". It either ate a chunk of metal to get that started, or there's just been too much thrashing in general going on. I'd replace the pair for third. Also, pay attention to the condition of the locking lugs on the sides of the gears. Be sure they are not worn or rounded, as this will cause the gears to separate and "skip" under a load. Check the forks for evidence that they are bent (contact between the fork ends). Lastly, check the bearings, especially the left side main shaft bearing.

If you are just riding MX, there's not much point in doing the 5 speed swap. The ratios are wider spaced, and low would be more or less completely useless for MX. If you geared for MX so that you basically could ride the entire track in 2nd, 3rd, and 4th, you might like it OK, but if you never play ride in areas where a wide range of speeds matters, again, there's no point in dropping $700 on the mod, really.

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