© 2013 Drake Smith - Please do not
use or reproduce this elsewhere. Feel free to link to it
Work w/o BMW Special Tools
According to BMW and other shop
manuals, you need a couple of special tools to perform
maintenance on K bike clutches. In reality, you don't.
Overview Of The Clutch
The following is a general
description of how K75, K100, K1 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.
Taking The Clutch Apart
As you take the clutch apart,
in order to mitigate introducing vibration into the clutch
assembly, it's a good idea to mark the rear pressure plate,
front pressure plate and clutch housing so that they can be
reassembled in the same rotational orientation to each other.
Removing Rear Pressure Plate
The rear pressure plate is held on by
six M7x25 bolts.
The Allen heads on these bolts are
somewhat shallow and if they were last touched when the bike was
assembled at the factory then they can be a bit stubborn to
remove. Therefore be sure to use a good, well-seated Allen
wrench when removing them. (Like the Heyco Allen wrenches in the
factory toolkit.) Heating them with a torch can help ease their
BMW recommends replacing these six
bolts and their lock washers with new ones when doing clutch
work but that's not necessary. I never have on the many clutches
I've dealt with and it's never caused an issue.
Once those six bolts have been
removed the front pressure plate does not "fall right off." It's
still held on with three pins.
A handy tool to use for working
around the perimeter to gently pry the pressure plate off is a
mini nail puller pry bar. You want to use a 5.5 in "mini" one as
larger ones won't fit.
Here's a few examples:
- Vaughan 222
- Dasco 222
- Titan 11505
When putting the clutch back together
the torque spec for the six clutch bolts is 19 Nm. (14 ft-lbs)
BMW Holder - Part 112800
The purpose of this special tool is to
hold the clutch housing in place so the you can
remove/install the clutch nut without having it turn the
By inserting a block of wood into
the upper left corner between the bellhousing and one of the
clutch housing flanges, you can accomplish the same thing.
BMW Clutch Centering (Alignment) Tool - Part 212670
The purpose of this tool is to
center the clutch plate before retightening the six clutch
bolts so that the splines of the clutch plate are aligned
with transmission input shaft when the transmission is
You can buy aftermarket machined
aluminum clutch centering tools on eBay for about $25
However, I developed my own
approach without the need for a special tool of any kind.
Namely, using the transmission itself as your centering
When you install the clutch
plate, tighten the six clutch bolts only enough to hold the
clutch plate in place by light friction but so that it can
still move. Then feel around the edges and use your fingers
to get it as well centered as you can that way.
Put the transmission in fifth
gear (makes turning the input splines via the output shaft
easier) and, without the pushrod in, temporarily install the
transmission, wiggling it around and turning the input shaft
until it mates with the clutch plate. Then push the
transmission all of the way on. The clutch plate is
now aligned. Carefully pull the transmission STRAIGHT
back and then, once it is off, tighten the six clutch bolts.
Before lubing the splines and
inserting the clutch pushrod, install the transmission once
more to ensure that the clutch plate is properly aligned
with the clutch bolts tightened. Then remove the
transmission, insert the clutch pushrod, lube the
transmission input splines and do the final transmission
© 2013 Drake Smith - Please do
not use or reproduce this elsewhere. Feel free to link
to it though.