Center case reboring?

2 replies to this topic
  • bryawn

Posted April 16, 2011 - 02:39 PM


Last week I traded an XR100 for an 04 YZ450F with a big hole in the right case by the kick starter. Since this area supports the kick starter, it is a fairly involved fix. One of the previous owners had fixed it at some point using a welded on piece of some sort. In any case, it didn't hold, and I don't want to be stressing about it breaking when I am out in the middle of no where. Ideally, I'd like to just replace the right side case.

So I know that the cases are line bored at the factory and that mixing and matching cases can be problematic since there could be misalignment where there are through bores.

But I an wondering if it would be possible to get a replacement right half on eBay and take both halves to a machinist and have him check it out and correct any alignment issues? What think. Has anyone done this? Or do I really have to get a full replacement on both cases?

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  • KTM-548cc

Posted April 16, 2011 - 03:05 PM


i seen people mix match cases on honda 2stroke with no problems that im aware of. i understand your concearn though and ideally they probly should be used as a matching pair. but i really doubt youll have a problem but its hard to say. if by some chance the bores didnt line up perfect, the only way to correct it is to weld and remachine. welding cases can be done but i dont recomend it unless its a last resort to the problem. the reason i dont recomend it is because if the welder isnt very skilled and know what hes doing youll have even more problems. had a cylinder welded once and i was chasing cracks all over the place afterwards. even with a skilled welder things can get dicey. i would probly find a cheap case half from ebay and not sweat it. have a machinist look them over if it gives you piece of mind but i dont believe youll have a problem.

  • bryawn

Posted April 18, 2011 - 08:12 AM


Thanks for your thoughts. I definitely don't want to start welding center bores etc. That seems like a very bad idea. I've been thinking the same lines that chances are it would be fine. It seems the cases come from the same molds, they are put on the same machines for boring, etc. How much variation could there be and would it make any difference in how the machine works? I'm guessing it would be fine.

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