My bike is a 78 R100(RS). I checked my total driveline lash, like you did in your initial post. I measure 1.5” in 1st gear, and 3.25” in 5th. My last shirtsleeve evaluation of my wheel spline was 1/3 worn. I do not experience any of the “bucking” sensation you describe.
I don’t know what to suggest. These bikes are pretty darn simple, so we know it’s not a computer issue or fuel injection glitch. It’s kinda like; does the engine turn?, is there compression?, do the valves operate and have proper clearances?, does the ignition and advance operate properly, and in time?, that leaves the carburetors. I wish someone would loan you a pair of carburetors to try in place of yours. Sounds like a lot of fooling around, but if you endured this growing issue for many years, no biggy to swap carbs.
I was in my nearest BMW dealership just yesterday. Someone brought in a bike with an issue; When shifting from 2nd to 3rd gear, the bike shuts off completely. Wow. An airhead could never pull that off.
The drive splines do have those steps deep inside that you mention. Having eliminated other possible causes I now feel pretty convinced that the bucking is caused by driveline lash there in those splines plus possibly elsewhere in the driveshaft and final drive. And I have located a local-ish mechanic evidently capable of the work! It's scheduled for November. Thanks to all of you for your dedicated input!
By the way, here's a comment and question on BMW motorcycle forums. In my early days the "forum" was the BMWMOA magazine. It was a treasure trove! I clipped technical articles and organized them by topic. Then 15 years went by without much motorcycling. When I got active again I re-subscribed to BMWMOA mag but it doesn't have technical articles like it used to. It's in forums now! And there's not just one!
- BMWMOA has one I haven't explored.
- I am getting familiar with Airheads, and it makes sense for me because I don't need anything post-airhead.
- There is one specifically for R65s, even more targeted to my needs, but it is small and not super-active.
- VintageBMW
- Adventure Rider
- Others?
It would be more convenient if they were all one, but so be it. Which do you all use, and for what purposes?
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.
Wear at the drive spline is mainly caused by lack of lubrication and water protection. A waterproof or water-resistant grease must be added to the splines each time the rear wheel is removed. The grease acts as a cushion and shock absorber, similar to the oil in a motorcycle roller chain.
IMHO, forces involved in drive spline wear can be reduced by using only modern synthetic lubricants in the gearbox, drive shaft and final drive housings. The oils and greases specified in the original owner's manual are woefully out of date.
See: https://bmwmotorcycletech.info/rearwhlsplines.htm
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
That Snowbum guy is amazing, what he puts out! I could spend hours on one if his articles.
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.
Yes, Snowbum … it sometimes takes hours. He has compiled a vast amount of information. Just takes some patience looking for the information you need at times. It was one of his rambling articles that jogged me to do further checking, that led to my “EUREKA!” moment with my carb issue. Thanks, Snowbum.
Are your splines original? If so, they have done well for 170k miles! You must keep them maintained nicely.
My splines are original. I've always dabbed anti-seize into them when replacing tires. I am relieved to see that there is a way to rebuild a spline drive without all new parts. Something they weld into place. Though new pinion and ring gear may be advisable too. We'll see what this new mechanic says.
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 agree with the 50% worn rate, that would figure in with the miles on the bike. LOL, I wore out my first set of splines at 95K but I have a lot of up and down shifting and a fair amount of stop and go.
I hate to say yes, this is the cause of your problem and have you spend a bit of cash to replace the spine units only to say "well that didn't fix the problem".
Another way to put it is to ask, is this rock and roll situation something you have to fix or can you adjust to it and get another bunch of miles on these splines changing them when they are 75% shot? of course if you do change them now and that solves the problem win win, you may not have to change them again and it is one less item to worry about.
How are you doing looking at some of the other items listed as being a cause? I know you cleaned and lubed the bean can insides and that didn't solve the problem but did help a bit? St,
Beware! I do not suffer fools gladly! St.
I think my splines are over 50% gone. I should get it done regardless. Re-doing the bean can felt very right but it didn't help the bucking. I'll have that mechanic do a valve leak-down test too. I bought new spark plug leads but haven't installed them yet. I don't see how they could be doing it but they're so old I suppose I should install the new ones as preventative maintenance.
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 am happy you have a shop that will do the splines, remember do both the wheel spline and the final drive spline, they must be done as a set.
As for wear, I used never seize for years without problems, applying it or redistributing it each time I change a rear tire. As I said, I am hard on the spines because of stop and start, lots of downshift. Someone who rides all day without this factor can have twice the lifespan. LOL, just like the people around here who don't ride in winter don't have issues with rust.
I don't know how many miles you put on a year but once done for the average you may not have to worry about them again.
My friend has an owner call him to pick up a bike from the side of the road. He has stopped, went to pull away and clunk, no go. That was the worst set of worn splines I have ever seen in all my years. Poor guy bought the bike (pretty looking) used rode it a few times and got bit bad with previous owner's disease. Seems the previous owner didn't know or care about spline lube. Oh yeah, the transmission input shaft needed to be replaced as it had not been lubricated and was shot. LOL fifty fifty as to which would have given out first.
You don't have that issue, pat your self on the back for doing the right thing. Anyway a long winded note, good luck keep us up to date. St.
Beware! I do not suffer fools gladly! St.
I am happy to report that I found a slightly used final drive and had it installed (along with other work). And the roll-on roll-off bucking is gone! The fault was entirely in the worn-out splines that drive the rear wheel. Along the way to this solution I also rebuilt the points-in-a-can, and am glad I did. Thanks to all for their input.
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.
Stephen, thanks for the follow up. Did you replace the splines on the wheel as well? They wear evenly so both should be replaced, unless you have a newer wheel with newer splines to go with the newer final drive.
LOL, now you can take time to find a shop to replace the spines in the old final drive and sell it. Glad to see things worked out. St.
Beware! I do not suffer fools gladly! St.
@14724 Only the final drive side of the spines were worn, not the wheel side. The fit is plenty tight in my mechanic's opinion.
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.
Well that is good news Stephen. Not to be a jerk but I am scratching my head as to why only the final drive splines would be worn out? I have had two sets replaced and each time had to have both sides done as they wore equally.
Maybe the spline on the final drive was different metal wise, softer than usual? Are you sure the wheel spline wasn't replaced at one time?
If I am off base, ignore me, LOL ride. St.
Beware! I do not suffer fools gladly! St.
Well that is good news Stephen. Not to be a jerk but I am scratching my head as to why only the final drive splines would be worn out? I have had two sets replaced and each time had to have both sides done as they wore equally.
Maybe the spline on the final drive was different metal wise, softer than usual? Are you sure the wheel spline wasn't replaced at one time?
If I am off base, ignore me, LOL ride. St.
Beware! I do not suffer fools gladly! St.
I suppose the wheel-side splines (they were original) weren't worn due to different metal. I think you can rivet new splines onto a wheel but Jason didn't think it was necessary. If he'd had a used snowflake wheel he would have sold it to me cheap, but he didn't have one.
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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