I have a 1975 CB550K that i picked up from a friends dad for cheap. This is my first bike and I got it running and driving and everything works great except i cant shift up. I have First gear and neutral and that's it. What can cause my issue. and how big of a job could it be to fix this issue. I have tried rolling the bike back and forth while trying to shift up and at different speeds and RPMs. and i rebuilt the clutch pack because the frictions and steels were stuck together.