thanks to all helpful bits so far , i,ve done this assembly many times , but i,d like to see if there are better ways , , is it better to fit bearings to cases then fit the shaft ? the yams i,ve had to disasemble have mostly been for tranny issues and when the bearing is tite on the crank and doesn,t need replacement i can,t see the point of going through the trauma of getting it off , how tite should they be ? all the bultaco,s i,ve rebuilt , the bearing / shaft fit is a lot less tight , also yamaha seals go castelation,s in , as far as i can tell from diagrams ( i have found them in some of my machines the other way round ) any confirmation ? the heavier seal lip would be inside ? tia