I am replacing steering stem ball bearings. The races for the originals had to hold ball-bearings, and were wide and really easy to remove: while the inner diameter of the fork tube (in the middle) is about 1.625 inches, the inside diameter of the bearing race is only 1.218 inches. So it protruded 0.2 inches from each side of the head tube, and it was easy to insert a drift into the head tube and put it against the rear lip of the old bearing races, to pound them out.
Now looking at the new needle bearings, the races have inside diameter only 1.638". This is a _bigger_ hole than the head tube itself (by 13 thou). That means when it comes time to replace these, the drift will just slide clean through the head tube without catching the back lip of the race. There will be no lip at all. I don't see how anyone would get these new bearings out.
I've seen youtube videos saying that newer bikes have two grooves ground into the head tube. If you get the drift into one of these grooves, it will catch the back edge of the race. I'm wondering if I should grind those into my head tube (with a dreml) before I insert the new bearings. If so, what positions would be best? (forwards/back, or side-to-side?), and how many thousands deep?
The head tube OD is about 1.935" (counting factory paint + rattlecan paint)... maybe 1.928 without paint? Minus the 1.625 ID, that's about 303 thou for both sides, or maybe 151 thou thick for each side. That would be about 9 gauge steel (149 thou). Thinning it by 25% on each side would be about 38 thou... but that's just barely over 1/32". It doesn't seem like enough to get any tool to catch it (maybe a flat-blade screwdriver with a tip that's been curved and sharpened).
Thinning by 3/32" seems like maybe enough, but that would be removing 94 thou out of 151 (42% of the metal in those two spots).
The old bearings don't look bad... I'm half tempted to just put in new balls and swap the races top-to-bottom (the bottom always indexes, the top just rusts).
I may be wrong, but if you are worried about replacing the tapered roller bearing races sometime in the future it seems to me that you are worried about something that probably will never happen. The tapered roller bearings have MUCH more bearing surface than ball bearings, so they will last a VERY long time; probably much longer than you need to worry about. So I highly recommend that you use all the proper pieces when replacing the steering stem bearings and not try to come up with your own solution.
I don't know what bike you own, but I replaced the ball bearings in my 1977 KZ650-C1 using All-Balls bearing and races and I can assure you that the new roller bearings work very, very much better than the old ball bearings. I replaced the races along with the bearings, and I really like them a lot!
If at some time in the distant future for whatever reason you want to replace the roller bearing races it can be done without too much fuss by simply cutting them and removing them rather than tapping them out like the original races. Ed
What bike is this on.
You can't swap the races on the 650/900 and 1000's as the bottom one is bigger than the top.
There plenty of meat to grind drift access points for the thinner walled taper races.
I use a diamond burr in 2 locations at 3 and 6 o'clock (side to side).
My bike is a '77 KZ400-D4 frame (with a '79 KZ400-B2 engine).
I'd thought about that welded panel, though I was wondering about just adding a washer behind the races. It wouldn't need to fit perfectly, so long as it was perfectly flat, and the races bottomed-out securely. The bottom race would actually be easier to drive in, since it wouldn't be recessed.
Anyways, I thought it was probably correct that a dreml could be used to cut them out, so I just drove in the races as-is, and if they need redoing in 10+ years, so be it.
If and when you get to the point you need to take the "new" races out all you need is to have someone weld up a bit of "slag" on the race on two opposite sides. That will give you two points to locate a drift or punch on and you can tap the race out. Just remember to work from side to side and not jam the race in the steering head trying to drive it out too quickly. Easy operation.