The Place

Is it possible to swap crankcase halves?
I have a couple of sets but due to different damage i was wondering if the top off one can be paired with the bottom of the other?

I wouldn't have thought so.
They would have been machined up as a matched pair ex factory.

Thanks, thought that myself

It has been done . Not by me but it did work.

Was that by good luck or considered measuring do you know.

If the gearbox is free and it most likely will be, then look at the mains. I have mandrels for most motors I have worked with over the years , two thou less than the main bearing journal sizes. If you bolt the cases together and the mandrel is solid then its a waste of time. If it turns even a bit tight ( dry ) then you try a mixture of fine lapping paste and penetrating oil on the mandrel and start lapping , gradualy tightening the cases untill its fully tightened. Then plastiguage the journals and see what oil clearences you have. You can generaly tell at the begining if its going to work or not. I didnt start with the mandrels for putting odd case halves together. The old Yamaha 600s could twist the cases in time and my R6s broke cranks at times so it was to check the journals to see if I needed new cases.

Thanks for the info.