What is this black magick?

[Puddles]

Uncle and I have been contemplating our clutches. His in an '04 R1100S Boxer Cup, and mine in a '96 R1100RT. The detail we are confussed and befuzzled over is: how the blazes does the clutch actuate? Mine seems to have something like a throwout ("clutch release") bearing, but there's a rod sticking out, and I can't wrap my head around what it may poke into. His... well, we look at the fiche image, and all I can think is that when you squeeze the clutch lever, the clutch must know what to do by osmosis, because we don't see any possible physical activation.

 

I'm sure once we have them in bits & strewn about the garage (for spline inspection), we will say AHA, but it just feels better to go in having some slight clue.

[dirtrider]

Uncle and I have been contemplating our clutches. His in an '04 R1100S Boxer Cup, and mine in a '96 R1100RT. The detail we are confussed and befuzzled over is: how the blazes does the clutch actuate? Mine seems to have something like a throwout ("clutch release") bearing, but there's a rod sticking out, and I can't wrap my head around what it may poke into. His... well, we look at the fiche image, and all I can think is that when you squeeze the clutch lever, the clutch must know what to do by osmosis, because we don't see any possible physical activation.

 

I'm sure once we have them in bits & strewn about the garage (for spline inspection), we will say AHA, but it just feels better to go in having some slight clue.

 

Afternoon

 

The clutch is released from the rear of transmission with a push rod that runs through the center of the trans input shaft. The push rod pushes on a pressure plate diaphragm spring therefore releasing the spring tension on the pressure plate.

 

Think of the BMW clutch as a backwards clutch to what you are used to. Instead of the clutch disk getting pushed forward into the flywheel by the pressure plate & spring it gets pushed backwards into a clutch cover (basically a flywheel on the rear of the clutch housing). When you activate the clutch lever it pushes the pressure plate forward away form that rear flywheel.

 

[Puddles]

Thank you!

 

I am so dim that I still do not understand how the push rod and "slave" cylinder exist in the middle of all this spinning tomfoolery. Isn't it like trying to reach through a spinning bicycle wheel/spokes to grab something on the other side? That trans input shaft does rotate, I know, because my bike goes, and goes, and goes....

[Jim Moore]

The pushrod goes through the center of the input shaft. The entire assembly is centered on the input shaft.

[dirtrider]

Thank you!

 

I am so dim that I still do not understand how the push rod and "slave" cylinder exist in the middle of all this spinning tomfoolery.

 

Isn't it like trying to reach through a spinning bicycle wheel/spokes to grab something on the other side? --Yes, sort of. But it doesn't grab it, it pushes on the spring center to push it forward to take pressure off of the pressure plate & allow it to move forward. It also doesn't reach through the spokes, it reaches through the very center of the wheel bearing (think of the bicycle wheel bearings with a hollow axle holding it with the push rod going through the center of that hollow bearing axle).

 

That trans input shaft does rotate, I know, because my bike goes, and goes, and goes--Yes, the pushrod goes right through the center of the spinning input shaft & through the center of the clutch parts. There is a bearing in the slave cylinder that allows the pushrod to spin without issue.

 

[Lowndes]

Puddles,

 

Are you SUUUUURE you want to take it apart just to inspect the splines?? I replaced my '99R1100S clutch (slave cyl seal failed) two years ago with the help of my brother (a long time bike mechanic) in his shop with a bike lift and every conceivable tool. It took several weekends. See pics. '99 R1100S Clutch Job.

 

You start taking parts off at the license plate and stop when you get to the crankshaft. And that's the easy part. Putting it all back together correctly, in the correct order with the correct wires, tubes, screws and bolts at the correct torques is the REAL test.

 

What about just pulling the starter and viewing the splines from the "starter hole"?? There are several good "How-To's" out there on this procedure. That's a two-hour job with tool kit tools and it can tell you if there is a prob or not. My splines were good, THANK HEAVENS because the fix for bad splines can be iffy and expensive. Also, if you go all the way in there you WILL want to replace the clutch friction disc, the slave cyl (and flush the hydraulics), drill the weep hole for the slave cyl, and might as well clean the TB's. While you are waiting on these parts and likely a few others, might as well remove the tank and replace the fuel filter and internal hoses and add QD's. It's not a "weekend job" for most.

 

 

 

 

[AndyS]

Puddles,

 

Are you SUUUUURE you want to take it apart just to inspect the splines?? I replaced my '99R1100S clutch (slave cyl seal failed) two years ago with the help of my brother (a long time bike mechanic) in his shop with a bike lift and every conceivable tool. It took several weekends. See pics. '99 R1100S Clutch Job.

 

You start taking parts off at the license plate and stop when you get to the crankshaft. And that's the easy part. Putting it all back together correctly, in the correct order with the correct wires, tubes, screws and bolts at the correct torques is the REAL test.

 

What about just pulling the starter and viewing the splines from the "starter hole"?? There are several good "How-To's" out there on this procedure. That's a two-hour job with tool kit tools and it can tell you if there is a prob or not. My splines were good, THANK HEAVENS because the fix for bad splines can be iffy and expensive. Also, if you go all the way in there you WILL want to replace the clutch friction disc, the slave cyl (and flush the hydraulics), drill the weep hole for the slave cyl, and might as well clean the TB's. While you are waiting on these parts and likely a few others, might as well remove the tank and replace the fuel filter and internal hoses and add QD's. It's not a "weekend job" for most.

 

 

 

 

+1

Also, with that starter off. you can get some lube onto that input shaft spline.

Here's what I do.

Make up a very runny mix of Molybdenum Disulphide (MOS2) powder and IPA (Alcohol).

Take care not to flood the area. You DO NOT want this on your clutch disc!

Ensure the bike is in 5th or 6th gear,

Start on the top spline.

Use an artists brush or pipette on an extension. Run some MOS2 onto the spline and work the rear wheel to encourage the MOS2 to wick along the spline. Then bump the rear wheel until the next spline is at the top. Repeat the procedure until all have had a sip of the MOS2.

 

[Puddles]

Thanks guys!

 

Inspecting, and lubing, the spline shaft is the primary objective here. And yes, throttle cables, fuel filter etc, drive line maintenance too. But your advice to do the spline inspection and lube through the starter port sounds splendid. I am not really agitated about the clutch parts at this point.

 

That trans input shaft does rotate, I know, because my bike goes, and goes, and goes--Yes, the pushrod goes right through the center of the spinning input shaft & through the center of the clutch parts. There is a bearing in the slave cylinder that allows the pushrod to spin without issue.

 

So, still, how does whatever pushes on the pushrod get past the spinning input shaft, that's what's got me.

 

[dirtrider]

Thanks guys!

 

Inspecting, and lubing, the spline shaft is the primary objective here. And yes, throttle cables, fuel filter etc, drive line maintenance too. But your advice to do the spline inspection and lube through the starter port sounds splendid. I am not really agitated about the clutch parts at this point.

 

That trans input shaft does rotate, I know, because my bike goes, and goes, and goes--Yes, the pushrod goes right through the center of the spinning input shaft & through the center of the clutch parts. There is a bearing in the slave cylinder that allows the pushrod to spin without issue.

 

So, still, how does whatever pushes on the pushrod get past the spinning input shaft, that's what's got me.

 

Afternoon Puddles

 

The trans input shaft is hollow all the way through the trans front to rear. (if you remove the push rod & slave cylinder you can look all the way through the input shaft from rear of trans to clutch spring.

 

So the push rod basically spins in the middle of the input shaft but is free to slide forward & rearward. The slave cylinder is bolted on the rear of trans with the slave piston bearing centered on that spinning push rod.

 

[Puddles]

The trans input shaft is hollow all the way through the trans front to rear. (if you remove the push rod & slave cylinder you can look all the way through the input shaft from rear of trans to clutch spring.

 

So the push rod basically spins in the middle of the input shaft but is free to slide forward & rearward. The slave cylinder is bolted on the rear of trans with the slave piston bearing centered on that spinning push rod.

 

This is plausible!

 

Except I do not have a slave cylinder, having a clutch cable...

 

I'm bemused to learn that BMW decided to reach ALL THE WAY THROUGH the transmission for this purpose, making a hollow output shaft just because they can. Oh! I've got it! Someone said "What on earth are we going to do with all these really long airhead pushrods, now that we're using overhead cams?" (but of course, they said it in German)

 

[dirtrider]

The trans input shaft is hollow all the way through the trans front to rear. (if you remove the push rod & slave cylinder you can look all the way through the input shaft from rear of trans to clutch spring.

 

So the push rod basically spins in the middle of the input shaft but is free to slide forward & rearward. The slave cylinder is bolted on the rear of trans with the slave piston bearing centered on that spinning push rod.

 

This is plausible!

 

Except I do not have a slave cylinder, having a clutch cable...

 

I'm bemused to learn that BMW decided to reach ALL THE WAY THROUGH the transmission for this purpose, making a hollow output shaft just because they can. Oh! I've got it! Someone said "What on earth are we going to do with all these really long airhead pushrods, now that we're using overhead cams?" (but of course, they said it in German)

 

Evening Puddles

 

It really has to do with powertrain length. To keep the engine/trans as short as possible the slave/or/throw-out lever needs to be mounted on the rear of transmission. That means the push rod must run through the trans input shaft to get to the clutch. The clutch also operates sort of backwards as the pressure plate moves forward to release (it's packaged inside the flywheel)

 

Lots of motorcycles run the pushrod through the trans input shaft, the slave just mounts on the side of trans not the rear as the clutch is on the other side.

[Jim Moore]

The trans input shaft is hollow all the way through the trans front to rear. (if you remove the push rod & slave cylinder you can look all the way through the input shaft from rear of trans to clutch spring.

 

So the push rod basically spins in the middle of the input shaft but is free to slide forward & rearward. The slave cylinder is bolted on the rear of trans with the slave piston bearing centered on that spinning push rod.

 

This is plausible!

 

Except I do not have a slave cylinder, having a clutch cable...

Your cable actuates a plunger that presses on the throwout bearing and moves the pushrod. The function is similar to the slave cylinder except it's cheaper, simpler, and more reliable. Which is why BMW went away from it.

[Puddles]

Your cable actuates a plunger that presses on the throwout bearing and moves the pushrod. The function is similar to the slave cylinder except it's cheaper, simpler, and more reliable. Which is why BMW went away from it.