Clutch Cable Adjustment Question

[dhgeyer]

1996 R850R, but I bet the same is true for any bike with a cable actuated clutch from this generation. The manual says that, to adjust the clutch, you set the top adjustment to a set amount (12mm from adjuster to nut as shown in the diagram), and then do the actual adjustment at the other end. I've had two mechanics tell me that it must be done this way.

Can anyone think of any logical reason why this would be true? I sure can't. How on earth could the clutch actuating pushrod (too lazy to look up the real name of the part) know which end of the cable has been adjusted? All it knows is how far it's being pushed in. If the top adjuster isn't there to be used, why is it there at all? It doesn't make sense.

Not to mention that it would be a lot easier to get the right amount of freeplay with the top adjuster!

 

[PGlaves]

Sure. BMW wants the clutch arm on the back of the transmission to be parallel to the back of the case - perpendicular to the clutch rod - at the center of the clutch arm throw. So they specify a top adjuster setting that extends sufficient cable at the bottom so that when the free play is set by the bottom adjuster the arm is in this parallel / perpendicular position. On the traditional K bikes they specified a cable length beyond the sheath at the bottom to accomplish the same thing.

This adjustment puts the least side loads on the throwout bearing assembly prolonging its life. So is it critical? Probably not! If the free play setting is correct the clutch will still fully engage and disengage. But, like most things in life there is a better way and a not quite so good way, and BMW has specified the better way.

Added: The process of adjusting is really pretty simple. Set the threaded gap at the top adjuster to 12mm. Then loosen the locknut and adjust the adjuster bolt at the transmission until the free play between the clutch lever and handlebar housing is 7mm. Then use your left hand to pull the clutch lever and hold it. Snug up the 13mm locknut with a wrench in your right hand. The pressure from the pulled clutch keeps the bolt from turning while you snug up the locknut.

 

[dhgeyer]

PGlaves: Thank you for your timely response. I just did the clutch adjustment, just as you, and the manual, describe, and it worked fine. It's just a bit awkward getting at the adjusters at the back of the clutch. I had to buy one special socket (deep 13mm) and one extender for the 10mm socket to get a wrench on the required nut/adjuster. If there's a way to get any other kind of wrench on those pieces of hardware, I can't imagine what it would be, at least on my bike. The only way in is from the back, and the rear suspension makes the length of the socket critical. I found it to be awkward.

Here I go again, a newbie questioning the expert, but your answer made a lot more sense to me the first time I read it than on subsequent readings. I'm going to make the assumption that the most frequent cause of excess clutch freeplay is the cable stretching, rather than the clutch plates wearing. Doing the adjustment as you, and the manual, describe changes the angle of the clutch arm relative to the rear of the case. Turn the adjuster in, and the free end of the arm moves away from the clutch case: back the adjuster out and the free end of the arm moves closer to the back of the clutch case. Since the pivoted end stays where it is, either movement changes the angle of the arm. Adjusting from the top would not do this. If what you say is true, wouldn't it make more sense to adjust at the rear only when/if the clutch plates are worn, or something else internal has changed, and, in the more frequent cases where the cable has stretched, leave the rear adjustment alone and compensate for the longer cable at the top adjuster?

Sorry to be a pain, but I like things mechanical to make sense to me.

 

[PGlaves]

PGlaves: Thank you for your timely response. I just did the clutch adjustment, just as you, and the manual, describe, and it worked fine. It's just a bit awkward getting at the adjusters at the back of the clutch. I had to buy one special socket (deep 13mm) and one extender for the 10mm socket to get a wrench on the required nut/adjuster. If there's a way to get any other kind of wrench on those pieces of hardware, I can't imagine what it would be, at least on my bike. The only way in is from the back, and the rear suspension makes the length of the socket critical. I found it to be awkward.

Here I go again, a newbie questioning the expert, but your answer made a lot more sense to me the first time I read it than on subsequent readings. I'm going to make the assumption that the most frequent cause of excess clutch freeplay is the cable stretching, rather than the clutch plates wearing. Doing the adjustment as you, and the manual, describe changes the angle of the clutch arm relative to the rear of the case. Turn the adjuster in, and the free end of the arm moves away from the clutch case: back the adjuster out and the free end of the arm moves closer to the back of the clutch case. Since the pivoted end stays where it is, either movement changes the angle of the arm. Adjusting from the top would not do this. If what you say is true, wouldn't it make more sense to adjust at the rear only when/if the clutch plates are worn, or something else internal has changed, and, in the more frequent cases where the cable has stretched, leave the rear adjustment alone and compensate for the longer cable at the top adjuster?

Sorry to be a pain, but I like things mechanical to make sense to me.

My experience is that once adjusted with a new cable the things seldom need adjustment. When they do, I usually find that the cable is damaged - strands are breaking, and the cable is beginning to unwind. At this point it is time to replace the cable.

Two things happen at once: as the clutch disk wears the free play decreases. If the cable elongates free play increases. Both of these things occuring over time leaves the adjustment somewhere near correct.

That said, if you want to adjust it at the top feel free to do so. I sometimes make little changes up there because the free play has changed a little. I don't think it makes a huge difference. But you asked the why of it, and my original answer provides the why. Bear in mind that as it swings the arm starts applying pressure before it is perpendicular to the clutch rod, and if fully pulled it is applying pressure after it is no longer perpendicular. The manual procedure provides a reference point that only minimizes the issue - it doesn't eliminate it.

 

[ANDYVH]

I have found the factory recommended technique to actually result in a better clutch feel and actuation. Even the setting of the gap at the barrel adjuster seems hardly relevant, until I read it explained by Mr. Glaves. So yes, it is the best setup for the clutch cable. I too have found I rarely have to adjust the clutch on my 94 R1100RS, until the clutch wear is causing a change in clutch actuation.

 

[dhgeyer]

Thank you PGlaves. Now it makes more sense. I think that what I'll do from now on is keep an eye on the position of the arm, adjusting there to keep it in the proper position as needed and as best I can measure it, and use the top adjuster if the arm is already correctly positioned and the freeplay is incorrect.