ugh sorry aboutthe sloppy posting but anywho,
This is a trick I learned from a guy who used to own a Bultaco dealership. If anybody remembers Buls well there apparently was a recall problem with the connecting rod set to tight and this guy rebuilt a lot of cranks under warranty<?>.
any how make sure everything is clean, cases soap and water clean. if you dissassemble the transmision put a light coat of STP or thick motor oil on the shafts before you assemble the gears. Put the crank,new bearings, and transmision in the freezer.
With all the bearing retainers removed from the bearings you want to replace, place the cases in the oven and cook them at 400 degrees farenhiet for an hour. With welding glose or good oven mitts pick up the cases most of the time the bearings will be left in the oven , if not one good slapping down of the case against some hard wood will knock them out. A quick wipe of a clean rag behind the old bearings and make sure there are no splinters of the wood stuck in the dowels. Drop your frozen bearings into the respective bores of the hot case with a slight tap of a hammer handle to make sure the bearings are seated and install any bearing retainers with blue loctite on the screws. Install your frozen crank and transmision< the light coating of STP is real sticky now help holding the gears on the shafts> in the right side case. Put on your gasket or gasket sealer. Line up the right side case with the crank and transmision shafts and drop it on. If there is less of a 1/4 gap around the case you should be ok to tighten up the case screws<in a criss cross pattern> to snug it down evenly and tight. I use a brass or wooden punch and just give a slight tap around all the bearing bores of the case and a slight tap with a rubber mallet all the way around the crankcase seam. Make sure your shirt front or gloves didn't get pinched in the seam, you will look kinda sillly walking to the tool box with an engine hanging off your belly looking for that case splitter you made earlier.
Assemble your shifter and make sure you have all the gears and spin the crank <it should always return to top dead center without a piston on it >making sure everything spins free and smoothly. When everything is cool double check screws tight and smoothness of rotating parts.
If you spend your time making sure everything is clean and organized before you start, it is truly simple and easy once you done a one or two. The guy I used to watch could have Bultaco bottom end from oven to complete in 20 minutes 1/2 hour.This I know works extremely well for 82 and 88 RMs <even though they tell you to build it in the left case for the shifter detent spring but a pair of long needle nose pliers takes care of that> and a 94 yz250. I am pretty sure it would work for just about anybike unless the heat of the crankcases will melt the inboard mounted seals<kawasakis I think>.