© 2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

Clutch 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.

When 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 removal.

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 engine.

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 re-installed.

You can buy aftermarket machined aluminum clutch centering tools on eBay for about $25 shipped.

However, I developed my own approach without the need for a special tool of any kind.  Namely, using the transmission itself as your centering tool. 

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 installation.

© 2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.