I have used M50 mid 1990s I recently purchased I was going to use the parts but I took a liking to the bike and recided to rebuild and keep it. So I am in process of complete overhaul on this baby. complete removal cleaning greasing of components, replacement of tires, grips seat etc.
My recent discovery was worn bottom bracket. I could not find exact replacement locally and did not want to wait for online order. I pulled old went to local bike shop
old was Schimano bb lp 25 with hard screw side on the non crank side of bike.
new bike shop gave me bb-un26 that looks like it fits but here is what happened.
connections on new are reversed from OEM typically you screw in the hard metal side into crank end and then put plastic non crank end left second. the new bb seems to screw in too much that the left end plastic screw cap wont tighten up to the frame. I have about 1/8 to 3/16 gap on left side.
I removed and matched up old to new and found the treads on new are deeper causing the assembly to dive into the frame thus causing right end crank to stick out.
My thought is to put some washers on the crank end right side to pull the assembly back out and see if the plastic end left will secure up to the frame.
How far out can I take the crank end shaft as to not mess up my chain and rear cassette function?
I did this with a Spalding Blade BB replacement the new did not give me enough space and small sprocket would almost hit the frame 1/8 washer seemed to fix it