Author Topic: K bike clutches  (Read 28817 times)

Offline frankenduck

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K bike clutches
« on: May 15, 2011, 12:52:35 PM »
This thread includes three sections on K bike clutches:

1 - How they work

2 - How to adjust them

3 - How to replace the clutch plate and/or O-ring



1 - How A K Bike Clutch Works

See K-BikeClutch.jpg below

The following is a general description of how K75, K100 and K1100 clutches work.  The basic design is the same although some of the individual parts vary between the models.

The clutch assembly is attached to the engine output shaft via the clutch housing. (Yellow)  In addition, the clutch housing provides some rotational inertia to the clutch assembly.

The clutch has two pressure plates. (Blue) The rear pressure plate is fixed to the clutch housing and does not move.  The front pressure plate “floats” on three flat arced springs around it’s perimeter. (Red)

The diaphragm spring (Purple) pushes the front pressure against the clutch plate (Green) and the rear pressure plate to engage the clutch.

When you pull in the clutch lever, the clutch lever arm on the back of the transmission pushes the clutch push rod (which goes through the transmission input shaft) into diaphragm spring and compresses it.  The front pressure plate can then “float” away from clutch plate and the clutch is disengaged.


2 - How To Adjust A K Bike Clutch

The following is a page from a BMW service manual that describes how to adjust the clutch:

See clutchadjustk.jpg below

This page is also attached to this thread as a PDF file at the bottom of this post if you want to print it out separately.


3 - Replacing The Clutch Plate or Clutch Nut O-ring

My procedure for doing this is attached as a PDF file at the bottom of this post.

UPDATE: Oct. 22, 2012: In my write-up I mention using a wider one of these to help pry off the outside pressure plate but a guy who I was helping with his clutch came across this thinner version which looks much better suited to the job.  It can' be found at Home Depot, Pep Boys and various places online.

Tool Choice 5" Utility Pry Bar  - Part number 17516 (see attached pics)


updated by scott_ 10-15-13 to update missing photo's
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline frankenduck

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Re: K bike clutches
« Reply #1 on: March 15, 2012, 04:24:19 PM »
Here's an example of using a block of wood to hold the clutch basket in place to torque the clutch nut.  Place the block of wood where the light blue square is to loosen the clutch nut.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline jimmyd

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Re: K bike clutches
« Reply #2 on: May 13, 2012, 06:39:41 PM »
Are there any special tools to remove the bolts in the rear pressure plate?
I'm using hand tools and my first couple of attempts ended in the entire assembly spinning while I tried it remove the bolts securing the rear pressure plate.
1994 K 1100RS

Offline frankenduck

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Re: K bike clutches
« Reply #3 on: May 13, 2012, 07:14:56 PM »
Look at the picture above your post.  The only special tool required is a block of wood.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline TimTyler

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Re: K bike clutches
« Reply #4 on: August 11, 2012, 06:09:19 PM »
Clymer recommends using a hammer handle for this (instead of a wood block). If you use a hammer, don't use one with a rubber or plastic handle as it will get chewed up.

I didn't feel like cutting a wood block to fit, and my hammer has a comfy rubber handle, so I used the non-U part of a bicycle U-lock which fit perfectly.

You'll also need a 30mm or 1-3/16" socket for the nut.

Offline Dbltour

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Re: K bike clutches
« Reply #5 on: February 04, 2015, 11:11:08 PM »
Bloody fantastic Tim!  Is that the OnGuard U-Lock you're using?
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Offline kris

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Re: K bike clutches/ Plate Thickness
« Reply #6 on: February 17, 2015, 09:45:44 PM »
Does anyone know what a new clutch friction plate measures in thickness (mm)? Mine is a shade over 5 mm and I've read elsewhere that I can safely continue to use this plate (as opposed to replacing it). I am very easy on clutches and don't ride bikes in an aggressive manner. Some said the plate should last the life of the bike.

Thanks!
  • In the Hammer!! Hamilton, Ontario, Canada
  • 1986 K100RT (Heinz) 2004 Kawasaki Concours (Eddy) 2007 Moto Guzzi Breva 1100 (Linda) Previous: 1968 Honda CD175 1973 Kawasaki S2350 1975 Honda CB550K
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Offline rbm

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Re: K bike clutches
« Reply #7 on: February 18, 2015, 12:18:47 AM »
New = 5.3mm +/- 0.25mm.  Wear limit = 4.3mm
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Offline kris

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Re: K bike clutches
« Reply #8 on: February 18, 2015, 07:14:18 AM »
Thank you Robert. You just saved me $45! I was reading elsewhere that the rivets are close to the surface, even on new clutch plates. For anyone looking for a new clutch plate I was in touch with a company called Euro-Drive Clutches Inc., out of Burlington, Ontario. They quoted me $45 to re-line the friction plate, which I thought was a great deal. The splines are in great shape on my disc. For guys in the US this is an absolute deal with the exchange the way it is now...20+  per cent. Check out www.euro-drive.com

Thanks again
  • In the Hammer!! Hamilton, Ontario, Canada
  • 1986 K100RT (Heinz) 2004 Kawasaki Concours (Eddy) 2007 Moto Guzzi Breva 1100 (Linda) Previous: 1968 Honda CD175 1973 Kawasaki S2350 1975 Honda CB550K
"I got bike fever bad!!"

Offline JVDH

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Re: K bike clutches
« Reply #9 on: April 19, 2016, 01:06:16 AM »
Does anyone tell me if it is recommended to replace the diaphragm spring when changing out the pressure plate, friction plate, and the pressure ring?

Also, has anyone had experience with the heavy duty, oil resistant pressure plates made of a kevlar material?

Trying to do all that is necessary for long life while it is open!

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Offline Scott_

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Re: K bike clutches
« Reply #10 on: April 19, 2016, 06:37:29 AM »
I think one of the critical items to replace is the rubber o-ring(#11 in the large diagram at the top of the post). It will be the cause of most engine oil related leaks in the clutch area.
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Offline johnny

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Re: K bike clutches
« Reply #11 on: April 19, 2016, 07:47:15 AM »
i replace everything with new oem... when the 1st one gives me approx a hundert grand miles of aggressive yeeehaaaa... the 2nd oem oughtta too too... caint see not replacing everything and f-ing with the other stuff...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline JVDH

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Re: K bike clutches
« Reply #12 on: April 19, 2016, 10:41:10 AM »
Cool, thanks for  the quick response.  I was looking into the kevlar (heavy duty/oil resistant) clutch plate due to the fact that the only reason I am replacing the clutch components is because of a rear main seal leak. (have only 32,000 miles on the bike)  Thought that getting the kevlar clutch plate instead of the OEM would prevent having to do that if the rear main seal leaks again...any thoughts?
  • Costa Mesa, CA
  • '93 K1100RS

Offline Laitch

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Re: K bike clutches
« Reply #13 on: April 19, 2016, 11:58:58 AM »
Kevlar clutch discs are made for hard track use. Stop-and-go can glaze them. Money intended for a kevlar disc should be diverted into buying fuel for riding. A leaking main seal will increasingly leak. Riding with one is wasteful and befouls road surfaces, even if a clutch disc could handle it.
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Offline johnny

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Re: K bike clutches
« Reply #14 on: April 19, 2016, 01:04:48 PM »
greetings...

ride it often and it wont leak in the 1st place... low miles is the problem... if it had a hundert grand or more on it you would be out getting some yeeehaaa instead of saying how few miles your 23+ year old motobricks has on the odo...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline JVDH

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Re: K bike clutches
« Reply #15 on: April 19, 2016, 03:58:27 PM »
Got it, thanks for the responses.

It sat with the previous owner, I put about 8k miles on it in the first year!  Just want to do things right while its accessible.

Had to replace the transmission, 2nd gear was no longer functioning.

Any insight into what the problem could be on the transmission?
  • Costa Mesa, CA
  • '93 K1100RS

Offline Laitch

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Re: K bike clutches
« Reply #16 on: April 19, 2016, 06:09:24 PM »
Any insight into what the problem could be on the transmission?
Not enough info on that one, JVDH, or interest either from my perspective. If you've got the old case, take it apart and work out the reason.

The time for riding is here. Button up that bike's drivetrain and go.
  • Along the Ridley in Vermont.
  • 1995 K75 80,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline jonas_105

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Re: K bike clutches
« Reply #17 on: June 06, 2017, 08:32:06 AM »
What size is the o-ring?


Thanks!
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Offline Laitch

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Re: K bike clutches
« Reply #18 on: June 06, 2017, 09:17:35 AM »
What size is the o-ring?
Welcome, Jonas! Put your bike's year in your profile.

* Clutch o-ring from MAXBMW parts fiche..png (52 kB . 511x256 - viewed 1019 times)
  • Along the Ridley in Vermont.
  • 1995 K75 80,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline jonas_105

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Re: K bike clutches
« Reply #19 on: June 06, 2017, 11:30:51 AM »
Thank you  :clap:
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Offline wally.fisher

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Re: K bike clutches
« Reply #20 on: June 06, 2017, 05:01:17 PM »
What size is the o-ring?


Thanks!
19 mm inside diameter 4 mm section = (27mm) dia.)


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Offline qwertymotobrick

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Re: K bike clutches
« Reply #21 on: March 07, 2018, 02:50:21 AM »
19+4 =23  or i am wrong?
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Offline Martin

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Re: K bike clutches
« Reply #22 on: March 07, 2018, 06:13:22 AM »
19+4+4=27
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