Here is a tool I made for my KLR650 that would work in this application too with different sockets. It's just a piece of all-thread and nuts and washers. This photo shows it with my old bearing races on there that I'm using as drivers since I have them, but if you're reusing your old races you don't need them to do the job. It's just nice to use if you do have them because they fit perfectly. If you're using old races, be sure you slit one side of them with a hacksaw or (easier) Dremel and cutting wheel so you can remove them from the bore of the frame after pulling your new race in! (Sometimes the bearings go flush with the frame, but on other bikes they are deeper in the stem, so your old one would pull right in too).
You can see how it works...first grease the OD of your bearing races and the ID of the frame. Then put one or the other race in the frame and tap it with a hammer a bit to get it started and make sure it's lined up. Then install this tool through the frame and put a socket that is juuuust slightly smaller than the OD of the race. The heavy black washer goes on the other side of the frame hole. If you don't have washers you could use a piece of steel with a hole through it, whatever you have that can act as a strong base for the tool to pull against.
Obviously you tighten the nuts until everything snugs up. Then check the alignment of your socket one last time and start turning the nut above the socket to pull the race down in. When you are sure it has gone as far as it's going to, remove the tool and, carefully, using a hammer and pin punch, drive around all the edges of the race to ensure it's fully seated. As others have said, you can hear and feel when it's in for sure. You get a much more solid "THUNK" and feel when the bearing is bottomed. Then, obviously, flip things over and do it for the other side.
Inexpensive tool and it works great. Make it once and it'll work on any bike you have. Make sure the all-thread you buy fits through the square drive of your sockets.
