1971 R75/5 weird clutch problem

[DonTom]

The clutch in my 71 R75/5, in the first quarter mile after a cold start, slips and makes noise to the point that the bike cannot climb up a slight hill a quarter mile from my home.

But after a few more seconds of slipping, the clutch holds perfectly and then I can easily go more than 100 miles (or as far as I want) with no trace of a clutch problem. I can even hold the clutch in at a steady speed up a slight hill and when I release the clutch out, the engine RPM will fall instantly back to the same RPM, just as it should.

This clutch problem is ONLY after the bike has been sitting over night.

What could my cold clutch problem be?

-Don- SSF, CA​

 

[toooldtocare]

First question, how much free play do you have at the clutch lever, and can you see free play at the release fork on the transmission? You should have some, at the lever I have about 1/8" gap between the frame of the clutch lever and the lever itself. If you do not have any free play, adjust it and try again. Maybe that the clutch swells due to the heat of slipping and works ok until it cools down again. I notice that the free play decreases on my bike as I ride and it warms up, indicating that the clutch plate does swell. So, I adjust the free play when it is hot.

Second question, do you see an oil slick between the clutch housing the engine housing? If so, you may have a rear seal going bad. This will cause the clutch to slip too, but it usually does not fix itself. Once the clutch is wet with oil, it stays that way until the leak is repaired and a new or reconditioned clutch disc is put in.

Wayne

 

[20774]

I would think that a clutch would be more likely to get oiled by a bad tranny input seal rather than a rear main seal. For the oil to get from the RMS, it's got to go completely around the flywheel but if bad enough I suppose it would get slung all around. Gear oil can easily get on the clutch disk since it doesn't have far to go. If there's any oil on the shelf below the tranny, that needs to be fixed, regardless.

Be sure the clutch is adjust per the "Tom Cutter" method that's been posted numerous times. Works great...less filling.

 

[toooldtocare]

I agree, a transmission seal will cause the problem, but I talk from experience about a rear main seal. My seal went bad a couple of years ago. The first symptom was an oil slick between the transmission and engine, then the clutch started slipping. Once removed I found everything in the housing was coated with a film of oil.

New "O" ring on oil pump, new rear seal, new clutch and all is well two years later.

Wayne

 

[Brettendress]

My $1,500.00 fix. Had similar issues replaced the cable cable lubed the splines thought I had oil on the disc. Turned out to be a rusty clutch plate and bad transmission bearings and play in the shaft so I rebuilt the whole thing and put in a new clutch. Call me a sucker but it took almost a year of what if it's this or that Now it runs like new and will be leaving for the Rally in a few days PS> Mine only acted up when hot ?

 

[DonTom]

First question, how much free play do you have at the clutch lever, and can you see free play at the release fork on the transmission? You should have some, at the lever I have about 1/8" gap between the frame of the clutch lever and the lever itself. If you do not have any free play, adjust it and try again. Maybe that the clutch swells due to the heat of slipping and works ok until it cools down again. I notice that the free play decreases on my bike as I ride and it warms up, indicating that the clutch plate does swell. So, I adjust the free play when it is hot.

If the free play decreases when hot, isn't that the opposite problem than what I have? But it won't hurt for me to check. I have not looked at the basic stuff yet.

Second question, do you see an oil slick between the clutch housing the engine housing? If so, you may have a rear seal going bad. This will cause the clutch to slip too, but it usually does not fix itself. Once the clutch is wet with oil, it stays that way until the leak is repaired and a new or reconditioned clutch disc is put in.

I think this could be the problem. I will take a close look later. I rode about 150 miles during the night. last night, so I have not yet took a close look at the bike in the light. But I have noticed my gear oil has dropped in level and I had to add some, and that was after I cleaned up the bike. I should be able to tell if I see any gear oil leaks when I look at the bike a little later.

Thanks, all, for the replies.

-Don- SSF, CA

 

[toooldtocare]

If the free play decreases when hot, isn't that the opposite problem than what I have?

You got me thinking, I am not sure. If you do not have any free play when cold that would be the same as pushing in on the clutch all the time maybe lifting the pressure plate off the disc a little causing reduced friction. Now, if the disc swells due to heat and pushes back on the pressure plate more, wouldn't it have more pressure, thus more friction? All I know is that I have to adjust my cable when hot, or the dimensions are not right. Long shot, but a simple thing to check. I would think that oil on the disc would cause slippage all the time. It did for me and your tests of dropping the clutch and getting no slippage when hot was the opposite for me. The engine would spin faster and the bike would not accelerate. Hope it is a simple fix, mine was not.

Wayne

 

[DonTom]

You got me thinking, I am not sure.

Perhaps we can be sure now. I just got back from checking out the bike and it was good news all the way around. The clutch has less than zero free play, so I bet that's the only problem. I also checked the gear oil and since the last tranny oil change (where it has used some, but it was a long time since I even looked at it) and it has not used a drop since ten, perhaps a thousand miles ago. Also no trace of gear oil leaks.

I will adjust it later and go for a test ride, but that might not be for a couple of weeks, as I will soon be leaving for my other home 250 miles away from my BMW.

BTW, I purchased this R75/5 new in May of 1971 for $1845.00.

Here's a picture recently taken:

http://s776.photobucket.com/albums/yy46/DonTom3/motorbikes/?action=view&current=BMW1.jpg

-Don- SSF, CA​

 

[toooldtocare]

New in 71, now that is something. Nice bike, and I hope your test ride is a success.

Wayne

 

[DonTom]

New in 71, now that is something. Nice bike, and I hope your test ride is a success.

Wayne

I just today got around to adjusting it and going for a test ride. Conditions were perfect. Cold and foggy here in the SF area tonight, and this problem was only after a cold start, especially on a cooler day.

Anyway, after the simple adjustment, all was perfect. The clutch engages sooner now, as it should. No noise, no slippage at all.

Over the years, I didn't even notice the difference in where it engages until after today's adjustment.

In my old age, I don't do as much maintenance as I used to. I used to check or adjust stuff to perfection so often that I never got to know the symptoms of things like the clutch free-play being out of adjustment.

Thanks for the help.

I am glad it was a simple problem which only had serious sounding symptoms.

-Don- SSF, CA

 

[DonTom]

Well, I have to take my previous message back! Today, I went for a ride and had the same problem at the exact same place again. At a stop sign before the top of the hill, about a quarter mile away.

Clutch made a lot of noise. Had almost no clutch at all. After the stop sign (it's still up hill) I want to go straight. But even at 5,000 RPM's the bike would barely move in first gear with the clutch fully out. So I was forced to make a U-turn and go down a short block and then came back to the same stop sign. This time, not even the slightest trace of any type of clutch problem. In a lot more riding today, no more clutch problems at all. This problem is only after the bike sits for a while and ONLY happens at that one stop sign when leaving from here.

A simple fix for now is to ride in the other direction for a half mile or so and then return to that stop sign. But I would like to know what causes this problem.

Now that I am sure the clutch cable adjustment is not the problem, what is next? And the clutch engages as soon as it should when the clutch level is released.

I assume something is getting wet when the bike sits for several weeks, but not always.

I hate these intermittent problems! Often cannot tell when they are really fixed.

-Don- SSF, CA

 

[toooldtocare]

Hate to hear this, it may be time to open it up. If the cable is adjusted right, than I do not think you can do much more until you get inside. Sorry.

Wayne

 

[bikerfish1100]

i agree with Wayne. if cable is properly adjsuted at lever and at tranny arm, then any other issue has to be with the clutch disc, or associated parts.

btw- if that's a recent pic of your bike- you need new fork seals.

 

[85k100lt]

Well

Sounds like the clutch is not releasing until a warmup. Throwout bearing, clutch pressures plate. Even may be a clutch cable binding. I would replace clutch cable first - cheap and an easy fix.

funny how the Fork seal comment popped up from your picture - but I had to go back and look and I see he is correct.

 

[lmo1131]

This problem is only after the bike sits for a while and ONLY happens at that one stop sign when leaving from here.

Sooo.. . never stop riding, and don't go to that intersection....

It's definitely time to "open up". Why waste any more time? If I lived in SSF I know where I'd take my /5, his shop is in Scotts Valley. If nothing else it was make a great spot to ride to... with your question.

And judging from the shiny spot on your rear tire (6 o'clock position), it looks like your Final Drive may have a problem as well. That, or your neighbor's pooch has a problem with BMWs. How well is your rear brake functioning; plenty of "stop", or not so much??

By the way, when did you install the Mikunis ...?

 

[DonTom]

And judging from the shiny spot on your rear tire (6 o'clock position), it looks like your Final Drive may have a problem as well. That, or your neighbor's pooch has a problem with BMWs. How well is your rear brake functioning; plenty of "stop", or not so much??

That might just be some water on the tire. I just washed off the bike before that picture was taken. I have not noticed any leaks there. The rear brake works fine, except it brakes a little too well for the first time used after the bike sits awhile. IOW, barley touch the brake pedal and it locks the rear brake, but only one time after sitting for months.

By the way, when did you install the Mikunis ...?

Many years ago. Perhaps was in the early 80's. The 1971 Bings were the junkiest carbs ever built, IMO. They would not idle when warm. 2500 RPM's was the minimum idle when the bike once got fully warmed up. And there was no real fix, other than replacing the carbs with something else. This bike also has two spark plugs on each side and a dyna ignition (but still with two six volt coils in series--still has waste spark).

-Don- SSF, CA

 

[DonTom]

i agree with Wayne. if cable is properly adjsuted at lever and at tranny arm, then any other issue has to be with the clutch disc, or associated parts.

Well, I assumed such anyway.

btw- if that's a recent pic of your bike- you need new fork seals.

Yeah, I know. It's about time. Those are the original 1971 seals. I also need to put on the boots.

How much hassle is it to replace the seals? Or should I bring the bike to somebody who knows what they are doing? And can I still buy all the needed parts, such as the boots and seals?

I assume so as 1971 don't seem all that old for a BMW, compared to some classics I have seen in this forum.

-Don- SSF, CA

 

[20774]

How much hassle is it to replace the seals? Or should I bring the bike to somebody who knows what they are doing? And can I still buy all the needed parts, such as the boots and seals?

To drop the sliders, not much more than getting the front wheel off. After you're removed a few bolts, the sliders will drop right off. The seals can be carefully wedged off so as not to scratch the mating surface. They easily go back on flush to the top of the slider.

I think BMW just stopped selling all parts for bikes built before 1972. Seriously, just about any part you need is available through your dealer network.

 

[DonTom]

To drop the sliders, not much more than getting the front wheel off. After you're removed a few bolts, the sliders will drop right off. The seals can be carefully wedged off so as not to scratch the mating surface. The easily go back on flush to the top of the slider.

I think BMW just stopped selling all parts for bikes built before 1972. Seriously, just about any part you need is available through your dealer network.

Thanks, that sounds like something I can handle. I will start the job soon.

-Don- SSF, CA

 

[dennisdarrow]

Yes, as Kurt mentions above one removes the front wheel; but a bit more than that...........We are talking about doing the /5 pictured above?.....Somewhat different than later models

Take off the front wheel and fender

Your gaiters are already off; but have you got the replacements.....CALL VETCH....

Remove the fill plugs at the top of the fork leg using the correct spanner/pin wrench

Take off the rubber "plugs" on the bottom of the fork

At the bottom of the fork, underneath, hold the allen with the appropriate size allen wrench and remove the nut and washer from each fork leg.

HAVE A PAN HANDY UNDER EACH LEG AS YOU ARE DUMPING YOUR FLUID

Grasp the bottom of the fork legs and PULL down.......SPLOOOOSH

Keep pulling after they have drained and the fork legs will come off.......for me, one at a time..........

Put the leg in a vice and remove the big cap on the bottom of the leg.

Clean out the cruddy/disolved bottom bumper junk

CLEAN, CLEAN, CLEAN the inside of the fork leg

Install NEW bumper

Using a new copper seal for the bottom of the leg and another sealing the big cap, install the cap on the bottom of the leg.................

The small copper ring goes on the inside of the leg held in place with a dab of grease.........

Put your new gaiters on

Slide the fork leg back on the slider

Install the bottom of the gaiter to the fork leg

Do the other leg

Push the legs up into place and reinstall the nut and washer to hold them in place

Take off the center stand to put full pressure on the bottom of the fork and torque the nut at the bottom of the leg

Back on the center stand

Install fluid to specified amount

replace bottom and top caps.................

GO HERE:
http://w6rec.com/duane/bmw/index.htm

I put the whole thing in cause you might use it or need it...........
Go down to the TELESCOPIC FORK SECTION and check out what he has to say...........


I am sure others will come forth with their total expertise and corrections; but the above is a pretty close outline of my thoughts on the procedure.......And yes, even this ol guy can do it for the first time in just an hour or so per leg......God bless..........Dennis