Sorry for a potentially saucy response, but I find it funny when people on internet forums tell me how bad my bikes are.
I have probably 50-60k miles on my 1974 transmissions with no problems. I did have two of them rebuilt just as a matter of refreshing them from a two-decade-slumber.
You all forgot about the smaller front axle, solid rotor (for R75 and R90), flywheel bolts, oil-pump cover screws, under-tank master cylinder, etc of the 1974s! Surely each thing alone would kill anyone who dared to ride one!
But guess what.. They're all fine bikes and there is no reason to avoid them. Yeah, someone who owned one three decades ago might have some horror story that's been endlessly perpetuated on the internet since then, but.. I currently own three almost-bone-stock 1974 BMW airheads and none of them have stranded me, let alone given me any 1974-year-based problems.
Originally Posted by JonO
Now it was not exactly an easy task to replace the transmission, but if you go slow, and stay patient, you can do it no problem.
I'll bet I could have one swapped out in 30 minutes.