Once again I am short of time but lets see if I can still get a few things in today.
Continuing with the transmission, the following photo shows the break down of the drive axle. First gear on the drive axle was found to have a chipped tooth. The corresponding gear on the pinion shaft was also bad. As 1st pinion gear is part of the shaft, the shaft is no good either.
Eventually I had both transmission apart and lying side by side. I made a table to tabulate the condition of each gear from the two transmissions and to help me keep track of what I was doing! My grading system progressed from bad to excellent using the notation X, check -, check, check +. I was to select check + (excellent) for all gears but I had to settle for a check (good) on the 4 and 5th gears on the clutch axle.
I noticed something else interesting involving the shift drums. These casings are hollowed out for light weight. The 1980 3R5 version appeared to be hogged out more than the 1981 4V4 version. Perhaps Yamaha felt the need for a strengthend part for some reason?
Let's go to the photos... top is 3R5 bottom is 4V4. Again, the 4V4 shift drum has the bearing on it since the selector star is welded rather than screwed on.
Both drums appeared to be in fine shape but I will use the 4V4 style in reassembly.