I have a 93 XR600 engine that has a problem with the cases. I have 2 sets of cases from an 86 and an 88 XR600. Can I take the guts out of my 93 and put them in the earlier cases? I'm talking everything from the crank to the countershaft. Are there any internal differences that will stop my plan? This is a long term plan. I was thinking of making a built XR600 engine. The first step will be taking the top end from the 93 engine and putting it on a 90 bottom end that I already have. Step two would be putting the 93 bottom end in the 80's cases and going high compression piston, cam , etc.