M20 bearing installation

[Gavin Housh]

Just checked out a thread from a Suzuki website that was about the changes in microstructure of bearing steel at anything over 250 degrees. I've at times had to heat my cases to almost 300 to get the bearings to drop out when gently dropping them onto a flat piece of wood. I guess 300 is ok for removing bearings and discarding them. If your trying to install M20 inner races on your crank keep them on the lowwer side of 250 or you will be changing the steel. This information comes from an engineer for a large Japanese bearing manufacturer so he should know his business. I just put a set of M20 inner races on and 200 degrees was fine. You just have to push them on to the stop as fast as possible. They cool quickly when they hit the shaft so don't hesitate. When installing M20 outer races in the cases I think it's fine to heat the cases to 250-300 and drop the races in. I wouldn't think the race would get hot enough to get over 250 before the case cools off enough not to be able to overheat the race. The engineer says that if the bearing reaches 300 it looses 10 percent of it's hardness. I heated my cases to 250 and the outer M20 races didn't drop all the way in on there own so I was forced to press them the rest of the way in. I think that idealy your not supposed to have to press them. Only just to make sure they are bottomed out in the bore. I notice the Penton Manual says to heat to 158-176 degrees, and my Clymer manual says 250-300, and my sachs manual says heat to 158-176. I have not had any luck with these lower temps. Interested to hear what others are doing. I also noticed in my clymer manual that the tool that is used to pull the inner races off the crank can also be used to somehow push the inners on the crank. Not sure how that works as my puller only pulls and is not in any way able to be used as a pusher?

[Dale Sonnenschein]

In the past I have heated bearings but was carful not to get them real hot. Not sure of the temp. I put bearings in cases and heated the case and put the bearing in the freezer for about 15 or 20 minutes and they fell together.

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r