I just intalled a set of mains and heat works very well for installing and for removing since the mass of the flywheel shaft and wheel will take longer to heat up with a heat gun than the race. It is winter here and one of the benefits is I get to use the oven in the Esse woodstove to heat up things. It has a good sized vented oven, big enough to take a comet crankcase half, and all the bad smells go up the flue, so no complaining is heard as oily parts heat up. I don't use a pan of heated oil but I don't have to get the bearings so hot that the oil in them dries out or gums up. Anyway, I have to say it is quite satisfying to drop the hot inner race over the cellar temperature mainshaft and hear it drop with a click all the way to the flywheel with no force required. I can't do a woodstove oven for removing them, but a heatgun works for that. If you have a good heatgun use the smallest nozzle that you can to concentrate the heat on the bearing.