If the gear is binding on the shaft, the most probably cause is damage to the bronze bush in the center. It's thin wall and often shows signs of damage at one end.
If it rotates part way and sticks, then the shaft is oval (not round) so check that between centers with a DTI.
How badly worn is the old 37t first gear? If it's OK to use that gear, do so.
trany swap
Moderators: oldjapanesebikes, H2RICK, diamondj, Suzsmokeyallan
I had bad bearings on the old trany and first gear dogs were chipped I was able to change first and the bearings so all is good now, the 37t gear (newer) I really didn't need but it was the problem if I were to change transmissions (thought I could just swap out tranys without any problems) anyway it's fixed now I'm saving up for pistons and getting the crank ready to sent out. Thanks for the help.