I am experiencing a problem with my cb77. I canot get it to upshift from first to second gear. apparently the shifter arm doesn't move the shifter drum all the way to the detent position , thus the shifter arm hangs up when i attempt to shift to second gear. There is a considerable amount of slop in the linkage outside the clutch cover but even moving the shifter arm manually [ with the clutch basket removed] produces the same result. Any ideas ?