1983 BMW R80RT needs a diagnosis, could be transmission problem

[pollbmw]

Hello!

I've joined the community to see if you can help me diagnosis my problem. The bike is a BMW R80RT, new to me, been driving for a year, about 80K+ on it. Over the winter I did a spline lube and replaced the rear main seal. Have been driving it around no problem.

The incident: going up a steep hill with my wife and I. Some idiot in font of me decided to come to a complete stop for absolutely no reason what so ever.. I have to come to a complete stop, but I don't do a great job of down shifting. End of reving the bike up pretty pretty high, wife an I both got the smell of something burning.

The symptoms: As I'm driving home I'm noticing some power vs RPM issues. I park the bike and walk away once I get home. A few days later I get on the bike and notice that I'm not getting the power I would expect going through the gears. Acceleration is really slow for the amount of RPMs I'm seeing. As I shift up through the gears I'm not getting the toque you'd expect... it doesn't feel like I'm getting what I'm supposed to as I shift through the gears, it takes forever to accelerate. Did not try taking the bike above 40-50 mph.

I removed the valve covers and got the gaps to .2 and .1 mm respectively, cold compression test is 125 lbs on both sides. Took the bike for a ride around the block, didn't fix my problem.

My fear is that I chewed up my transmission, not really sure regarding next steps on figuring out the problem.

Anyone have suggestions/opinions?

 

[52184]

Hello!

I've joined the community to see if you can help me diagnosis my problem. The bike is a BMW R80RT, new to me, been driving for a year, about 80K+ on it. Over the winter I did a spline lube and replaced the rear main seal. Have been driving it around no problem.

The incident: going up a steep hill with my wife and I. Some idiot in font of me decided to come to a complete stop for absolutely no reason what so ever.. I have to come to a complete stop, but I don't do a great job of down shifting. End of reving the bike up pretty pretty high, wife an I both got the smell of something burning.

The symptoms: As I'm driving home I'm noticing some power vs RPM issues. I park the bike and walk away once I get home. A few days later I get on the bike and notice that I'm not getting the power I would expect going through the gears. Acceleration is really slow for the amount of RPMs I'm seeing. As I shift up through the gears I'm not getting the toque you'd expect... it doesn't feel like I'm getting what I'm supposed to as I shift through the gears, it takes forever to accelerate. Did not try taking the bike above 40-50 mph.

I removed the valve covers and got the gaps to .2 and .1 mm respectively, cold compression test is 125 lbs on both sides. Took the bike for a ride around the block, didn't fix my problem.

My fear is that I chewed up my transmission, not really sure regarding next steps on figuring out the problem.

Anyone have suggestions/opinions?

Sounds like you may have a clutch that is slipping. Start with a complete fresh adjustment on the clutch, this link will provide you with an excellent guide to that procedure.

Best,
DeVern

 

[20774]

Welcome to the forum! Two things that I'd probably do. First, drain the transmission fluid and look at the magnetic drain plug...typically it will probably have some grayish fuzz on it, unless something bad happened and larger chunks are stuck to it. See what that tells you. Second, what does your clutch actuation feel like? Is the hand lever still engaging at the same point as you let it out? Maybe you need to recheck the clutch cable adjustment. Look at the link in my signature line and find the General Maintenance section. There are two links that provide basically the same info for setting up the clutch release mechanism.

 

[pglaves]

I believe the clutch is slipping. Why? Maybe lubricated with gear oil or engine oil from a bad seal. Maybe a worn clutch disk.

 

[MichiganR80RT]

Does it feel like the clutch is slipping? From your description of a burned smell and slow acceleration vs RPM the clutch is the prime suspect. At least if you have done a main seal you know how to get to the clutch.

I have had two drivetrain problems with my 1984 R80RT (about 150k miles total). Twice the final output bearing on the transmission in was bad. The first time was when I got the bike. It had been stored for more than a decade and there was rust in the bearing. The second time was about 90k miles later. Both times I heard bearing whine while riding and heard a clicking sound when I turned the drive over with the bike on the center stand. There were metal flakes on the transmission drain plug magnet both times.

The second problem was a bad bearing in the final drive. This felt like the bike was low on power and some I heard some bearing whine. The final drive also felt warmer/hot after riding.

My suggestion for troubleshooting would first be to ride it slowly and listen for bearing sounds. Afterwards feel for warm spots in the bearing areas. Then put the bike on the center stand with the rear wheel off the ground. Use a strap or zip tie to hold the clutch disengaged and turn the wheel over by hand. It should turn fairly easily and smoothly. Listen for grinding or clicking noises beyond the normal noise of the gears. If you hear something use a stethoscope to get a better idea of the location. Pull up the parts images online and see if there is a bearing where you hear noise.

You should also drain the oil from the final drive, driveshaft, and transmission and look for metal flakes. The transmission should have a magnetic drain plug.

If the transmission and final drive turn smoothly with no excessive noise your problem is likely the clutch. I replaced the half worn clutch and the rear main seal both times I had the transmission out because I was that far into the disassembly. Also, if you had a leaking main seal you may have gotten oil on the clutch plate which could cause it to slip early.

 

[20774]

gwolter -

As a bit of an aside, you had the two output shaft bearing failures. One you indicate might be due to the rust, but then you had another one. By any change, is your '84 model considered a late model year bike? Was it built say in the summer of 1985, making it almost an '85 model? There was a transmission bearing change, or specifically a circlip omission, that is more prevalent in '85-95 models. Anton mentions it here:

http://largiader.com/articles/circlip/

And Snowbum has been looking to capture production numbers to see when the missing circlip showed up:

https://bmwmotorcycletech.info/transmission.htm

Curious to see if this might explain your situation.

 

[dduelin]

If engine rpms no longer match the road speed you are used to - say instead of 3500 rpm in 5th and 55 mph or whatever speed 3500 rpm matches the clutch is slipping. It's usually worse in the higher gears. It might not slip in 1st or 2nd but might in 3rd, 4th and 5th. You can also diagnose a beginning problem with a worn or oiled clutch by getting up to a good speed in 3rd, 4th, or 5th and completely wide opening the throttle. If the rpms increase but mph doesn't increase correspondingly the clutch is slipping.

 

[MichiganR80RT]

gwolter -

As a bit of an aside, you had the two output shaft bearing failures. One you indicate might be due to the rust, but then you had another one. By any change, is your '84 model considered a late model year bike? Was it built say in the summer of 1985, making it almost an '85 model? There was a transmission bearing change, or specifically a circlip omission, that is more prevalent in '85-95 models. Anton mentions it here:

http://largiader.com/articles/circlip/

And Snowbum has been looking to capture production numbers to see when the missing circlip showed up:

https://bmwmotorcycletech.info/transmission.htm

Curious to see if this might explain your situation.

My R80RT was built in 1983, I think in November.

 

[20774]

gwolter -

Thx...I guess that settles that!

 

[pollbmw]

Thanks for all of the great advice on how to proceed forward!

Looks like I'll be picking up some gear oil tomorrow and doing a clutch cable adjustment!

Once done I'll report back my findings!

 

[stevenrankin]

Slipping Clutch

When you changed the rear main seal, how did the clutch disc look? Was there a lot of oil from the leaking seal sprayed around? Did any get on the disc? Sometimes, even after "cleaning" a disc, there is still enough oil to cause slipping. So even if the disc has plenty of pad on it, being saturated with oil, it might slip.
What did you use to lubricate the input spline? The wrong lube material might just migrate to the clutch.
You mention adjusting the clutch cable.

I don't mean to insult your skill as a mechanic however, I find when I have a problem right after I have worked on something, it usually is caused by the last thing I worked on or something in the neighborhood.

If you have not had major problems with the transmission, I very much doubt something has gone wrong internally with it. There is no harm in changing the gear oil and looking for chips or nasty metal on the magnet. It sounds more like perhaps the cable is out of adjustment or the clutch disc is oil soaked.

I really hope for you the problem is just an out of adjustment cable.

I am looking forward to what you find the problem to be. Cheers, St.

 

[guenner]

Over the winter I did a spline lube and replaced the rear main seal. Have been driving it around no problem.

Sounds like the work done was not causing an immediate problem. So far I have not read anything that would point to a slipping clutch.

I'm not getting the power I would expect going through the gears

Fuel supply? The hard stop slosh particles around in the tank and clogging the in-tank filter?

Breaks? Brake pad/shoe dragging, brake piston stuck from the hard stopping?

/Guenther

 

[pollbmw]

Reporting back: Problem solved!

I did not do a good job of adjusting the clutch cable when I re-installed the transmission . The cable was tight without a lot of free play, even after adjustment. I happened to have a new clutch cable laying around and when I compared it with the old one I found that the new one was about 10mm longer, so I installed it and followed this guy's video: https://www.youtube.com/watch?v=l0Nrjoo6c0s. Drove it around the block and it was back to normal.

I suspect I've taken a bit of the life out of my clutch plate and will likely want to replace it over the coming winter.

I'm not going to both draining the gear oil since this solved the problem.

I would like to thank you all for the guidance .

 

[pollbmw]

When you changed the rear main seal, how did the clutch disc look? Was there a lot of oil from the leaking seal sprayed around? Did any get on the disc? Sometimes, even after "cleaning" a disc, there is still enough oil to cause slipping. So even if the disc has plenty of pad on it, being saturated with oil, it might slip.
What did you use to lubricate the input spline? The wrong lube material might just migrate to the clutch.
You mention adjusting the clutch cable.

I don't mean to insult your skill as a mechanic however, I find when I have a problem right after I have worked on something, it usually is caused by the last thing I worked on or something in the neighborhood.

If you have not had major problems with the transmission, I very much doubt something has gone wrong internally with it. There is no harm in changing the gear oil and looking for chips or nasty metal on the magnet. It sounds more like perhaps the cable is out of adjustment or the clutch disc is oil soaked.

I really hope for you the problem is just an out of adjustment cable.

I am looking forward to what you find the problem to be. Cheers, St.

I agree that when you're trying to solve a problem check the last thing changed, and in this case it was the cable which was part of the overall project. For the record I used Honda M-77 Assembly Paste as the spline grease and I was NOT overly generous with it. Just a thin coat over the splines.

 

[20774]

Glad you found the video...I thought we were going to get through the whole video without an f-bomb being uttered. I should have known better!!

That is a good view of the procedure...it was the same as given in the links above. Nice to see it if someone is not familiar with the locations and adjusters. As a final check, when the hand lever is half way through the pull, the lever at the back of the transmission should be around parallel with the back plate of the transmission.

 

[stevenrankin]

Happy day!

I am glad you found the problem and it was a simple fix.

As I said, I don't mean to insult your mechanical skills, I have done things and had to go back to do them again.

I hang around a Airhead shop and see lots of stuff come in due to owners misconceptions of how to do things or what products to use for what.

Obviously, you used a correct spline lube. I meant no disrespect brining it up, I have seen wrong products used which migrated to the clutch.

As for changing the clutch this winter, I have to ask why? For the little bit it was slipping I would bet you didn't take all that much off of its life span. Life is too short, ride and worry about it when you have adjusted its last adjustment and it is slipping. Hopefully that will happen in the fall just before you put it up for the winter. Then it can be a winter project. Depending on how much you ride, you may get ten years out of the current clutch plate.

If during this riding season, it is still slipping and can't be adjusted, then of course change it this winter.

Happy riding, cheers, St.