At 148k miles my 1979 R65 started developing roll-on / roll-off bucking. At 174k miles I ran a thread here (see "Roll-on roll-off bucking") to discover its cause and found that it was lash in the drive train, especially in the final drive due to wearing teeth. I replaced the final drive with one with very few miles on it. The lash went away but 5k miles later the lash is back. Is it because the teeth in the final drive and in the wheel are a matching set and both should be updated at the same time (get a new wheel or repair the splines on it)? Or has some other component started to wear, like the drive shaft spring and coupler? What do people with high-mileage bikes do about drive-train lash?
My first BMW was a 1971 R75. I've had my 1979 R65 since 1982. I've had a BSA Bantam and a Kawasaki 200 along the way too.
I remember your first go around with this issue. I just sent off my final drive (‘78 R100) for rebuild with new output splines. Mine were about 50-60% gone with nearly 100k miles since last rebuild. The splines in the wheel are fine. I believe those are very rarely replaced, as they seem to be nearly permanent. However, with all the spline wear plus 170k on my transmission gears, I have never experienced any kind of roll-on/off bucking or symptoms like you describe. ( One thing I do not have is the cushion drive driveshaft).
Every bike has driveline lash. The gearbox itself has quite a bit. But, you say it went away for 5K miles. Perplexing to me. I still gravitate toward the carburetors/throttle/intake system. Secondly, the ignition - what system is in the bike? I experienced a faulty control module on an aftermarket ignition where the ignition advance was unstable - now that made for some bucking!
I had a R100 single-sided with 80K miles in which the large rear wheel bearing had gone bad. (This would be the same physical set up as your R65.) The large bearing controls the depth of engagement of the ring gear into the drive shaft pinion, which would have resulted in increased "gear lash".
Experiments with various final drive oils and their running temperatures after that repair convinced me to use only synthetic multi-grade gear oils. Apparently, the single-sided final drive housing is a very tough working environment. I interpreted decreased operating temperatures as decreased friction rates and thus more efficient power transmission.
I ended up using only Valvoline 75W-140 gear oil after that.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
@4949 It's the stock mechanical ignition advance in a can.
My first BMW was a 1971 R75. I've had my 1979 R65 since 1982. I've had a BSA Bantam and a Kawasaki 200 along the way too.
@wobbly What do you mean by single-sided? What would double-sided be?
My first BMW was a 1971 R75. I've had my 1979 R65 since 1982. I've had a BSA Bantam and a Kawasaki 200 along the way too.
@wobbly What do you mean by single-sided? What would double-sided be?
Single rear shock absorber (mono-shock) vs. the older models (/2, /5, /6 & /7) with double (L & R) rear shocks.
I was thinking the R65 came both ways. Maybe not. I'm not an R65 expert.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
So, stock 1979 was “points-in-a-can” ignition. I’ve never dealt with one of those. I presume the advance is still then mechanical with spinning weights and springs. With all the miles you have gone you must be well acquainted with the workings of that thing. So I’m probably stating the obvious, but if the mechanical advance is dirty/sticky it could behave spastically.
You know, I’m mis-reading your post. You said the driveline lash is back, not the roll on/off bucking. Oops! Sorry about that.
@wobbly It's got two rear shocks. I'm not aware of any R65s having a mono-shock.
My first BMW was a 1971 R75. I've had my 1979 R65 since 1982. I've had a BSA Bantam and a Kawasaki 200 along the way too.
@4949 While I was looking for the cause of the bucking I took apart my points-in-a-can (which you're not supposed to be able to take apart). I installed new springs and O-ring and re-greased it. This had no effect on bucking or performance
My first BMW was a 1971 R75. I've had my 1979 R65 since 1982. I've had a BSA Bantam and a Kawasaki 200 along the way too.
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