Originally Posted by disston
Here's one problem mentioned by Mr Bum but it's not the one I'm looking for;
One last bit of information about the cylinders needs to be made here. In the later 1980's, BMW added a sort of "step" machined into the cylinder spigots, and a similar matching step was in the crankcase opening. If you try to fit late cylinders to an early bike, you MUST machine-off the step.
Ummn, yeah. That step winds up in the pile of chips when you turn the spigot to fit the 97mm openings in the /5 block.
All the 500cc through 1000cc cranks are dimensionally identical (except R65 and R45 which is it's own animal). I promise you, there isn't a counterweight clearance issue.