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1973 R75/5 Back-to-road Project
- Thread starter anotherbmw
- Start date
anotherbmw
New member
Cylinder stud survived 150 mls, but...
I rode an easy 150 mls today. The stud repair seems to be a full success, no oil leak round the cylinder and no strange noises, which is good!
However, since I awakened the sleeping beauty from basically a 20-year nap, other little things pop up. I have a small oil leak at the clutch lever at the back of the transmission, oil is running down the lever and also the cable (see pic, the yellow color is motor oil). Then there is a tiny puddle in the "bathtub" behind the transmission. In total that resulted in maybe 5 drops underneath the bike after a 150 mls ride, so not really that bad.
My 2012 R1200R had sat for a while, which caused the rear engine seal to leak. Could that be the same problem here? If I continue driving it, assuming the leak doesn't get bigger, can I do any harm? Could oil get on the clutch plates?
As always, thanks for any input! By the way, next repair is planned, I already ordered fork springs and will also have to do the steering bearings.
I rode an easy 150 mls today. The stud repair seems to be a full success, no oil leak round the cylinder and no strange noises, which is good!
However, since I awakened the sleeping beauty from basically a 20-year nap, other little things pop up. I have a small oil leak at the clutch lever at the back of the transmission, oil is running down the lever and also the cable (see pic, the yellow color is motor oil). Then there is a tiny puddle in the "bathtub" behind the transmission. In total that resulted in maybe 5 drops underneath the bike after a 150 mls ride, so not really that bad.
My 2012 R1200R had sat for a while, which caused the rear engine seal to leak. Could that be the same problem here? If I continue driving it, assuming the leak doesn't get bigger, can I do any harm? Could oil get on the clutch plates?
As always, thanks for any input! By the way, next repair is planned, I already ordered fork springs and will also have to do the steering bearings.
Attachments
Olaf -
As for the oil on the clutch lever, you can follow the oil up to see where it's coming from. Likely, it's coming from inside the transmission, leaking past the seal...it's #6 in this diagram:
https://www.realoem.com/bmw/enUS/showparts?id=0260-EUR-04-1973-2476-BMW-R75_5&diagId=21_0071
As for the oil behind/beneath the transmission, you would need to get to the oil to figure out where it's coming from. If it has a sulphur smell, then it would be gear oil leaking past the input shaft seal to the transmission. If it is determined to be engine oil (no sulphur smell), then it would the rear main seal. Quite the project to get to the rear main seal. Note warnings to block the crankshaft from moving forward before removing the flywheel to get to the rear main seal.
Oil coming from the transmission usually runs down the front face of the transmission housing, but can travel forward along the clutch pushrod. In that case, it could foul the clutch disk. Leaks from the rear main seal typically wouldn't get on the clutch parts, unless it's flailing all over the place.
As for the oil on the clutch lever, you can follow the oil up to see where it's coming from. Likely, it's coming from inside the transmission, leaking past the seal...it's #6 in this diagram:
https://www.realoem.com/bmw/enUS/showparts?id=0260-EUR-04-1973-2476-BMW-R75_5&diagId=21_0071
As for the oil behind/beneath the transmission, you would need to get to the oil to figure out where it's coming from. If it has a sulphur smell, then it would be gear oil leaking past the input shaft seal to the transmission. If it is determined to be engine oil (no sulphur smell), then it would the rear main seal. Quite the project to get to the rear main seal. Note warnings to block the crankshaft from moving forward before removing the flywheel to get to the rear main seal.
Oil coming from the transmission usually runs down the front face of the transmission housing, but can travel forward along the clutch pushrod. In that case, it could foul the clutch disk. Leaks from the rear main seal typically wouldn't get on the clutch parts, unless it's flailing all over the place.
anotherbmw
New member
Kurt, Thanks for the detailed explanation. I have the feeling that a transmission removal is on my list at some point........I will take a good look in the next days, clean everything up down there, ride for some miles to get a better feel where the leak originates from and if it indeed is engine oil only or transmission oil as well.
Set aside a weekend and order parts
I would order new seals for the transmission, have a look at the neutral switch as well, rear main seal, oil pump housing O-ring, drive shaft boot and fresh gear oil. Then wait for a rainy or in-climate weekend and dig into it. With a good manual, decent tools, a little patience & luck you can get it done in two afternoons.
I wouldn't worry a whole lot about some drips and small puddles so long as you check the transmission and motor oil before you go for a ride it should be fine until you can get in there and stop the leaks. My R 90/6 leaked pretty good when I got it and I put about 2,500 miles on it before I pulled it apart and replaced the rear main and oil pump O-ring.
When you do the job MAKE DARN SURE YOU BLOCK THE CRANK SHAFT BEFORE YOU REMOVE OR EVEN LOOSEN THE FLYWHEEL.
I would order new seals for the transmission, have a look at the neutral switch as well, rear main seal, oil pump housing O-ring, drive shaft boot and fresh gear oil. Then wait for a rainy or in-climate weekend and dig into it. With a good manual, decent tools, a little patience & luck you can get it done in two afternoons.
I wouldn't worry a whole lot about some drips and small puddles so long as you check the transmission and motor oil before you go for a ride it should be fine until you can get in there and stop the leaks. My R 90/6 leaked pretty good when I got it and I put about 2,500 miles on it before I pulled it apart and replaced the rear main and oil pump O-ring.
When you do the job MAKE DARN SURE YOU BLOCK THE CRANK SHAFT BEFORE YOU REMOVE OR EVEN LOOSEN THE FLYWHEEL.
anotherbmw
New member
Sounds like a plan! I'll start reading up on it!
brook.reams
B Reams
This would be be a sign they are leaking. The clutch dust has become encrusted on the inside of the bell housing along with a damp area under the oil pump housing. Although this picture was taken after removing the flywheel, you can see this kind of crud and damp spot with it still installed on the crankshaft.
Best.
Brook Reams.
anotherbmw
New member
I checked out your website already, great documentation, will definitely use it as a guide! Thanks!
cwroady
New member
brook.reams
B Reams
cwroady
New member
brook.reams
B Reams
Chris,
Cool beans. I believe your will find a write-up showing all the parts, in order, for the throw-out lever assembly.
Best of success in keeping you '72 on the road.
Best.
Brook.
anotherbmw
New member
A few more little projects lined up.....
I did some reading and decided I will pull the transmission at some point soon (maybe in the freezing TX winter
) do do at least the following, since the bike has sat so long:
Replace main seal, transmission seal and oil pump seal and grease transmission splines, inspect clutch. Anything else while I am in there? I will buy some special tools, like main seal puller, transmission tool, at this point in my life motorcycle repairs need to be fun!
While I still educate myself about how to tackle that big project I'll do the following:
More to follow, stay tunded! And please keep the great advice coming!
I did some reading and decided I will pull the transmission at some point soon (maybe in the freezing TX winter
) do do at least the following, since the bike has sat so long:Replace main seal, transmission seal and oil pump seal and grease transmission splines, inspect clutch. Anything else while I am in there? I will buy some special tools, like main seal puller, transmission tool, at this point in my life motorcycle repairs need to be fun!
While I still educate myself about how to tackle that big project I'll do the following:
- Replace fork springs (ordered progressive springs already)
- Take off oil pan to check for any bits and pieces that may have ended up in there from my stud job (I really don't expect any, but better safe than sorry)
- While having the pan off I'll check the screen and of course will change oil and filter
- Replace steering bearings. They are sticky in the center position and I can't live with that. On my last 3 old bikes (Harley, CB, KZ) I have replaced them, it always made a bit difference. I already ordered the race pulling tool, so no beat up knuckles this time!
More to follow, stay tunded! And please keep the great advice coming!
On my /7, I had the same feel with the steering around the center position. It was mostly when I was turning onto streets into my neighborhood...the bike would just suddenly rotate after sticking for a bit.
I ended up pulling the steering stem out and essentially cleaned and greased the bearings while in place. The old grease had just dried up. It's been fine for quite some time now.
I ended up pulling the steering stem out and essentially cleaned and greased the bearings while in place. The old grease had just dried up. It's been fine for quite some time now.
brook.reams
B Reams
I did some reading and decided I will pull the transmission at some point soon (maybe in the freezing TX winter
Replace main seal, transmission seal and oil pump seal and grease transmission splines, inspect clutch. Anything else while I am in there? I will buy some special tools, like main seal puller, transmission tool, at this point in my life motorcycle repairs need to be fun!
SNIP ...
There are 3 transmission seals, the front, rear and shift lever, so I'm not sure which one(s) you plan to replace. If it's the front seal, around the splined input shaft, you should have the special seal install tool to prevent harming the seal as it goes over the splines. A "hack" is to wrap the splines with masking tape and push the seal over them. I've not done it that way, so can't comment on how well this works.
If you are not careful installing the front seal, you can dislodge the internal seal spring that keeps it tight on the shaft, and likely have a transmission lube leak thereafter. The special seal install tool has two parts, a cup the fits over the spline the seal slides over and an outer driver that drives the seal home. I borrowed these from an ex airhead mechanic I know. I've not seen them available from Cycle Works. An alternative would be to have your local dealer install the seal using the correct tools ... that is if they have airhead tools still on their special tool rack.
The very large rear seal can be removed and replaced. That said, BE VERY CAREFUL to not score the taper on the output shaft. That has to be pristine to hold the output flange tightly. Go slow, heat the aluminum housing around the seal, then protect the output shaft taper with some rags and pull the seal.
Hope this helps.
Best.
Brook Reams.
anotherbmw
New member
I am thinking that if I have to go in there anyways I'll replace them, doesn't cost too much and I will done for a good while.
At this time I am not sure either. The shifter seal seems fine, the front seal I guess I will only know once I have taken the transmission off.
In my world, removing and reinstalling the lower bearing and race were more than I felt like tackling. Nothing wrong with at least checking the race after clean up to decide if you want to go further. Of course, if you need to replace them and don't have them with you, then you're down for a bit.
My approach is that if something is a major pain to get out or inside of, then do all you can while there. If you can get back to it with not much hassle, maybe waiting until next time could be a possibility. YMMV!
anotherbmw
New member
I consider it a decent hassle to get the front forks out of there, so I ordered the race extraction tool and hope that I will get the bearing off the stem without a special tool. Then I can forget about the steering for a while. I will most likely damage the bottom dust cap, but I would replace that one anyway.
anotherbmw
New member
Fork springs being changed!
I tackled the fork springs. Here is what I did:
I bought a 36 mm nut and ground it down to remove the chamfer (Is that what it's called?) (see pic 1). I did it on a grind stone, it's not as perfect as you would get it on a lathe but did the job. The fork top nut under the cap is very thin and I wanted to avoid damaging it.
I hit the nut with a breaker bar. It would not budge at all. Luckily I had an impact driver available which did the job, but barely. The top nuts were in there pretty good, it probably wouldn't have hurt to use penetrating oil...
When pulling the spring I realized that my new progressive springs from BMW are about 2 inches shorter than the springs I pulled out there. I didn't expect that. What should I do? Add a spacer? And what would I use for a spacer, a piece of 3/4 inch PVC pipe?
I tackled the fork springs. Here is what I did:
I bought a 36 mm nut and ground it down to remove the chamfer (Is that what it's called?) (see pic 1). I did it on a grind stone, it's not as perfect as you would get it on a lathe but did the job. The fork top nut under the cap is very thin and I wanted to avoid damaging it.
I hit the nut with a breaker bar. It would not budge at all. Luckily I had an impact driver available which did the job, but barely. The top nuts were in there pretty good, it probably wouldn't have hurt to use penetrating oil...
When pulling the spring I realized that my new progressive springs from BMW are about 2 inches shorter than the springs I pulled out there. I didn't expect that. What should I do? Add a spacer? And what would I use for a spacer, a piece of 3/4 inch PVC pipe?
