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#1013325 - 06/22/18 08:27 PM Clutch slave cylinder  
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The Fabricator Offline
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Petaluma
I have a 2000 R1150GS. I would like to replace the 24 mm clutch slave cylinder with a cylinder with a larger cylinder to reduce lever force and broaden the 'engagement' zone of the clutch. I also have a R100/7 with a cable operated clutch that I fabricated a pulley system which halved lever force and doubled the engagement zone. [A larger engagement zone is useful when pulling out of sand and crawling around rocks.]

I realize I will have to fabricate an adapter plate and push rod extension [unless there is a longer push rod someplace. [Note to self: fabricate a push rod.]] I have looked at the space between the transmission and a frame member, and there may be enough space.

The question is: Has anyone done it? Know of it being done?

Maybe there is a master with a smaller piston. I would not like to have to deal with the switches, etc. Another model?


Tom, The Fabricator.
#1013337 - 06/22/18 10:51 PM Re: Clutch slave cylinder [Re: The Fabricator]  
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dirtrider Offline
The Oracle
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Originally Posted by The Fabricator
I have a 2000 R1150GS. I would like to replace the 24 mm clutch slave cylinder with a cylinder with a larger cylinder to reduce lever force and broaden the 'engagement' zone of the clutch. I also have a R100/7 with a cable operated clutch that I fabricated a pulley system which halved lever force and doubled the engagement zone. [A larger engagement zone is useful when pulling out of sand and crawling around rocks.]

I realize I will have to fabricate an adapter plate and push rod extension [unless there is a longer push rod someplace. [Note to self: fabricate a push rod.]] I have looked at the space between the transmission and a frame member, and there may be enough space.

The question is: Has anyone done it? Know of it being done?

Maybe there is a master with a smaller piston. I would not like to have to deal with the switches, etc. Another model?


Evening Tom

I'm not sure that you will broaden the 'engagement' zone as that is a function of clutch friction & deflection. You will add more clutch lever travel so you will have more hand movement to get to the engagement zone & you will have move hand movement through the engagement zone . You will also have more lever movement on each shift so that will change the shift to clutch timing.

The dry clutch on the BMW oilhead has a nice engagement zone & they function pretty good as built. I haven't ever heard of anybody trying to change it with any sort of functional gain in mind.

If you do decide to try it remember it is more than just a larger piston as the release bearing is built into the piston so you will need a piston with a built in release bearing.

If you go much larger on the slave piston then you could easily run out of stroke on the master cylinder as the travel is fixed & limited. Same with going smaller on the master cylinder piston as that will limit displacement volume going to the slave. You will also end up with the lever farther from the grip to get the same clutch action (most riders want it closer to the grip not farther)

Might be easier to just change the lever pivot to master cyl piston geometry to get the longer lever movement without effecting the hydraulic displacements.

It sounds like you are sort of new to that bike, I'm betting that once you get fully up to speed on that hydraulic clutch feel that you will not want to change it. Some like to move the lever to grip position closer to the grip but that is also limited due to piston stroke requirements.

If your lever has the little rotation barrel to change clutch lever position you can remove the barrel & grind the stop so the 0 position is usable but on some bikes that limits total clutch disengagement on a hot overworked clutch.


D.R. ___
Sent from my rotory dial wall phone!
#1013348 - 06/23/18 01:01 AM Re: Clutch slave cylinder [Re: The Fabricator]  
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Lowndes Offline
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Roswell, GA
Beemer Boneyard has aftermarket slave cyl's and some of them may be different diameters. You could enquire. It might be easier to find a smaller master cyl.

All of my hydraulic clutches have very easy lever resistance. Are you sure everything else is OK in there??

There is a rather close fitting housing for the slave cyl as part of the rear tranny housing. See pics. You may have to bore that out to fit a larger slave cyl and that would be a project.

My '99 R1100S slave cyl failed and the DOT4 ate up the clutch and the tranny seal next to the slave. While you are in there I'd recommend drilling a weep hole in that slave cyl housing to prevent killing your clutch when the slave piston fails. Remember: the CLUTCH THROW-OUT BEARING is part of the slave cyl piston (very small) and it is turning at ENGINE SPEED whenever the engine is turning, clutch lever in or out. It obviously has a higher load with the lever IN, but it's still turning when it's out as well. That little bearing can't last forever.

Outside view of the weep hole:
[Linked Image]

From the inside:
[Linked Image]


Old Fart Newbie
#1013349 - 06/23/18 01:05 AM Re: Clutch slave cylinder [Re: The Fabricator]  
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Tri750 Offline
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CA
You may even check ebay to see if any of the Chinese part cloning suppliers make "dogleg" levers for your bike.
They are incredibly inexpensive copies of brands such as Pazzo or CRG alloy levers.
The cantelever lever lessens effort and yet is adjustable, in fact they have I think 5-6 "clicks" of adjustment for fine tuning.

What are these items, "sand and rocks" you mentioned ?


Classic Cycle Connection
Current:
1971 R75/5 roadracer
1973 Kawasaki Z1 roadracer
1976 BMW R75/6
1999 BMW R1100RT
2007 Kymco People 200S

#1013375 - 06/23/18 06:17 PM Re: Clutch slave cylinder [Re: The Fabricator]  
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The Fabricator Offline
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Petaluma
DR sez
I'm not sure that you will broaden the 'engagement' zone as that is a function of clutch friction & deflection. You will add more clutch lever travel so you will have more hand movement to get to the engagement zone & you will have move hand movement through the engagement zone . You will also have more lever movement on each shift so that will change the shift to clutch timing.

I think my wording could have been better. I agree that what would happen is add more clutch lever travel. That is my goal [and reducing lever force]. I just find it easier to pull out of sand, etc. [For a demo, watch this] https://www.youtube.com/watch?v=Yx4vABlSpp0
I am aware of running out of lever travel. My fabricated pulley system for the old R100 [1/2 lever force reduction, 1/2 pressure plate movement] almost ran out of lever travel. In fact, the clutch did [does] drag a little. [Still less than ALL wet clutches do.] This time I would probably go for a 30% force reduction, which I calculate is a 27.3mm slave piston. So somewhere around 27 or 28 would be about right.
I thought about off setting the pivot in the clutch lever. Eccentric bushings. I remember thinking that was impractical! [Like fitting a different slave cylinder IS PRACTICAL!] I should make some measurements. I suspect a 1 or 2 mm off set might do it. I going to investigate that more thoroughly. I'll post if there is anything worth while.
Lowndes sez
There is a rather close fitting housing for the slave cyl as part of the rear tranny housing. See pics. You may have to bore that out to fit a larger slave cyl and that would be a project.
I thought about boring out the hole for the slave. Depending on the size of the slave cylinder, the wall might not be thick enough. That is where the adapter plate comes in. The plate bolts to the transmission, the slave bolts to the plate. Different bolt hole patterns and spacing. The slave wouldn't project into the transmission. This thread about a different, larger slave is about finding out if someone has done it or knows of it being done. The pulley system on my old R100 is a known modification.
Why re-invent the wheel? [Figure out what someone else already has.]

My '99 R1100S slave cyl failed and the DOT4 ate up the clutch and the tranny seal next to the slave. While you are in there I'd recommend drilling a weep hole in that slave cyl housing to prevent killing your clutch when the slave piston fails.

As far as a weep hole WHEN [your word choice]slave piston fails, I'm down with that. My slave has yet to fail, but the transmission seal has! And of course, I only discovered that when the clutch started slipping. The way I see it, the only way to drill a hole there is to remove the trans. I see in your photo the trans is out of the bike. My [interim] solution was to slot the gasket. I was able to attach a shop vac to the trans rear [slave removed] and suck most of the oil out of the push rod hole in the shaft. I then removed the starter, bind the clutch lever to the grip, select a gear, turn the wheel to rotate the clutch while simultaneously spraying 1/2 can of carburetor cleaner at the clutch/pressure plate interface. Now the clutch doesn't slip too bad. I haven't really ridden too much and am expecting a replacement in the future. But it may 'heal'. The clutch on my old R100 has slipped for more than a decade [175,000 total miles on the clock], so maybe a happy ending? Right now I am building a fairing, switching shocks, making seats, yadda, yadda and will probably maybe might disable it in the distant future to lube/replace transmission splines, swing arm bearings, final drive bearings, drive shaft bearings and what ever else goes wrong with these bikes.

Beemer Bone Yard has smaller piston slaves. Wrong direction. I want bigger.

Thanks for your comments.

Attached Files

Tom, The Fabricator.
#1013376 - 06/23/18 06:22 PM Re: Clutch slave cylinder [Re: Tri750]  
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The Fabricator Offline
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The Fabricator  Offline
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Petaluma
Originally Posted by Tri750
You may even check ebay to see if any of the Chinese part cloning suppliers make "dogleg" levers for your bike.
They are incredibly inexpensive copies of brands such as Pazzo or CRG alloy levers.
The cantelever lever lessens effort and yet is adjustable, in fact they have I think 5-6 "clicks" of adjustment for fine tuning.

What are these items, "sand and rocks" you mentioned ?


These are found in areas between asphalt slabs.
https://www.youtube.com/watch?v=rWAtScA2J-0


Tom, The Fabricator.
#1013452 - 06/25/18 12:37 AM Re: Clutch slave cylinder [Re: The Fabricator]  
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Posts: 467
Lowndes Offline
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Lowndes  Offline
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Joined: May 2016
Posts: 467
Roswell, GA
Hey, Fabricator,

Very interesting vid of your campsite in DV!! You really learn to appreciate tables and chairs when camping. Not to mention ROOFS and running water. Clean flat places are very handy for cooking, too.

"The way I see it, the only way to drill a hole there is to remove the trans." Not really. I did drill mine with the tranny out to get an idea about the angle I needed to drill the hole. It CAN be drilled without removing ANYTHING from the bike, if you know where and at what angle to drill. If you are unsure, you could remove the slave cyl (without removing the hydraulic lines but removing the rear wheel for access). The correct angle is a direct line thru the gearshift linkage to the housing. It requires a 9" or 12" hex extension and a 1/4" hex drive drill bit (1/16" to 1/8" dia bit). It would also require a long punch to start the hole because you are drilling at a slight angle to the housing to intercept to bottom of the slave cyl housing "hole".

"Slotting" the slave cyl gasket is an option, but I think it would only serve as a "telltale" for you that something is leaking, not as a "drain" to keep all the DOT4 or tranny lube from getting to the clutch.
Not many people would check that area very often so that might not prevent a clutch job. The clearance between the slave and housing is maybe 1/32" annular space and the gap in the gasket would be 0.002" (0.050 mm) by whatever gap you cut in the gasket.

The compromise alternative is to cut (file) a notch in the rear edge of the housing wall (the gasket seat). That would provide more opening than the slotted gasket.

I measured 1/4" gap between the slave cyl and the tranny seal so you have a large target (gap or void) there, but that might vary.

The OEM friction plate on my bike absorbed (and swelled) with the DOT4 and tranny lube. I doubt your clutch will get any better unless it is a Seibenrock Oilproof. Friction from slipping may overheat things and cost more for parts.


Old Fart Newbie

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