My 1979 R65 now has 175,000 miles on it. I do my own maintenance, so I am thrilled to to discover this club dedicated to just that model! Perhaps you can help me with an annoyance.
I’m quite sure my bike did not originally do this, and that it developed slowly over time. Say I am coasting in gear with the throttle closed. It can be in any gear at any RPM but it is most annoying at low speed. When I crack the throttle open any amount the bike lunges forward. When I close it again it decelerates in reciprocal manner, with a jolting suddenness. Thus I call it the “roll-on / roll-off bucking or lurching”. It happens 100% of the time. There is no clunk or noise. It is severe enough that when rounding a corner at low speed it disturbs my balance.
I have twice completely rebuilt the carburetors and replaced the throttle cables. This did not help. The idle circuit is clear of obstruction, so it’s not that. Someone said it is “drivetrain lash.” But when I put it on the centerstand, in gear, and rotate the rear wheel it only turns two inches measured at the tread. Internet postings, for various makes of motorcycle, indicate that this isn't excessive. What say you?