splitting cases ????

4 replies to this topic
  • mxdad32

Posted November 29, 2007 - 04:52 PM


I have an 07 yz450f and am splitting the cases. Do you have to remove the oil pump and oil pump gear before pulling the cases apart? It doesn't look like it but I want to be sure. I know I can just take them off and not worry about it but if I can I would like to split the cases first, if they don't have to come off first.

Thanks in advance

  • brt 426

Posted December 02, 2007 - 12:07 AM


When I stripped my yz426 I didn't need to remove the oil pump to split the cases. But I did remove the oil pump to clean it , before I reassembled the engine. And filled it with fresh oil . I imagine the 450 would be similar to the 426

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  • mxdad32

Posted December 02, 2007 - 07:51 AM


Thanks, I went ahead and removed it before splitting just to find out I didn't have to. I was going to remove one way or the other but was just curious as the owners manual while very good, does not really say one way or the other as far as I could see.

  • 642MX

Posted December 02, 2007 - 01:25 PM


Why are the cases being split?

  • mxdad32

Posted December 02, 2007 - 04:04 PM


We had been experiencing a problem for about a month with the oil coming out black at change time, which is usually every 2-3 hours. I did a top end rebuild and put in a new clutch basket/hub/plates and springs and the oil still came out black. There were also a few more metal particles than normal. Not wanting to have a catastrophic failure, I decided to tear it down all the way. After splitting the cases, where I expected to find a bearing going out, I found both second gears were black and the one on the main shaft to be pitting. Everything else looked like new. I will be replacing all bearings, the two gears and all of the collars and c-clips in the tranny and putting it back together. The bike had about 79 hours on it when I split the cases. The track that we practice on is basically a second gear supercross style track so I guess that is probably the cause. The bike was still running and shifting great at the time.

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