As someone who has been riding/repairing/rebuilding motorcycles pretty much all my life, and has frequently encountered this "problem", here is my solution. Use a retaining grade of Loctite, up here it would be 609, or something like that. Clean the bores in the frame very, very carefully. Then clean them again. Get a long piece of threaded rod, studding, whatever they call steel rod with thread all over, in your neck of the woods, some suitable nuts, and some big washers that are bigger than the o/dia of the races. Length of the studding should be 50mm or so longer than the length of the headstock. Then clean the steering head stem again, and clean the bearing outer races. Apply the Loctite EXACTLY i.a.w. instructions. Assemble the race outers in the headstock, and clamp in place with the studding, washers and nuts.
As long as you stick to the instructions this works every time. Personally the thought of centre popping to provide a press fit leaves me rather cool, especially for a classic like your BMW!
best of luck
cheers
Bill
As long as you stick to the instructions this works every time. Personally the thought of centre popping to provide a press fit leaves me rather cool, especially for a classic like your BMW!
best of luck
cheers
Bill