21 BMW R75/5 Install New Clutch

When I removed the clutch and measured it, I decided to replace it as most of the parts were worn to minimum tolerances.  You can read about how I removed the clutch here:

21 1973 BMW R75/5 Clutch Removal and Inspection

I purchased the new clutch parts from Tom Cutter at Rubber Chicken Racing Garage including:

21 21 1 250 035 Diaphram Spring (Heavy Duty)
21 21 1 251 801 Pressure Plate
21 21 1 236 332 Clutch Plate
21 21 1 231 666 Compression Ring
21 21 1 231 463 Filister Head Cap Screw (6)

Preparing for Installation

Here is a picture of the old and new clutch parts.  The new parts include an updated design for the compression ring and the clutch plate.

Old (top) & New Clutch Parts

Old (top) & New Clutch Parts, Inside to outside, Left-to-Right

The new compression ring does not use the spacers but has thicker sections at the edge.

Old Cover Plate with Spacers

Old CompressionPlate with Spacers

New Cover Plate without Spacers

New Compression Plate Without Spacers

The new clutch plate has more rivets than the old one.

Old (top) & New Clutch Plate

Old (top) & New Clutch Plate

The parts need to be cleaned before installation and I used brake cleaner. I also use long bolts, M8 x 1.0 x 35, to help assemble the clutch and three 1/4 inch diameter wood dowels, 2 inches long to support the parts until I can get the long bolts threaded. I use Honda 60 Molypaste to lubricate the diaphragm plate where it contacts the face of the flywheel and the tips of the fingers where they contact the pressure plate. I use the metal bar I made to keep the flywheel from moving when I removed the clutch to hold it when I torque the clutch bolts. And, I use a torque wrench on the clutch bolts.

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Supplies and Special Tools to Mount the Clutch

1/4 inch Wood Dowels, 2 Inch Long

1/4 inch Diameter Wood Dowels, 2 Inch Long

Here’s the junk I removed from the new clutch parts.

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Junk Removed from New Clutch Parts

Lubricating the Diaphragm Spring

To reduce wear, I put a thin amount of Honda 60 Molypaste on the edge of the diaphragm spring where it touches the face of the flywheel and on the edge of the fingers that contact the back of the pressure plate. I put on Nitrile gloves and I used a flat toothpick and just a little molypaste on it.  I cleaned the edge of the diaphragm spring to remove any molypaste that got on the edge.

Toothpick Application of Thin Layer of Honda 60 Molypaste to Edge of Diaphragm Spring

Toothpick Application of Thin Layer of Honda 60 Molypaste to Edge of Diaphragm Spring

Toothpick Application of Thin Layer of Honda 60 Molypaste to Edge of Fingers of Diaphragm Spring

Toothpick Application of Thin Layer of Honda 60 Molypaste to Edge of Fingers of Diaphragm Spring

Mounting the Clutch on the Flywheel

I put the three dowels in every other clutch hole in the flywheel and then placed the diaphragm spring against the face of the flywheel with the fingers facing me.

Clutch Diaphragm Spring Against Face of Flywheel

Clutch Diaphragm Spring Against Face of Flywheel

I removed the gloves and used a clean pair to continue the work. I don’t want to get any of the molypaste on the other clutch parts. I mounted the pressure plate with the hub against the diaphragm fingers and hung it on the dowels.

Clutch Pressure Plate Hanging On Dowels Against Diaphragm Spring Fingers

Clutch Pressure Plate Hanging On Dowels Against Diaphragm Spring Fingers

Then I put the clutch plate in the center of the pressure plate making sure it is facing the correct direction and hung the compression plate on the dowels and secured it with the long bolts so the washer is against the compression plate followed by the nut. I screwed the bolts in finger tight.

Clutch Plate with Spline Ring Facing Outward

Clutch Plate with Spline Ring Facing Outward

Compression Plate Hanging on Dowels with Long Bolts Attached

Compression Plate Hanging on Dowels with Long Bolts Attached

I tightened the long bolts tight enough that I could move the clutch plate and center it by eye but not so loose that it would move easily.

"Eyeball" Centered Clutch Plate

“Eyeball” Centered Clutch Plate

Centering the Clutch Plate

I removed the wood dowels. I used the transmission to center the clutch plate.  I hung it from the stud on the top right of the engine and then pushed the clutch plate until it lined up with the transmission input shaft.  Then I rotated the transmission input shaft just a bit until the splines lined up and I could insert the transmission input shaft into the clutch plate.  I added the other transmission bolts and adjusted the transmission so it was as far into the clutch plate splines as it would go.  The heads of the long bolts prevent it from going all the way.

Mounting Transmission to Center Clutch Plate

Mounting Transmission to Center Clutch Plate

Mounting Transmission to Center Clutch Plate

Mounting Transmission to Center Clutch Plate

I eyeballed the alignment of the transmission with the engine housing so it was centered left to right. Then I used an open ended 13 mm wrench and tightened the nuts on the top two long bolts to secure the clutch plate and then removed the transmission carefully to avoid disturbing it.

Tightening Nut to Hold Centered Clutch Plate

Tightening Nut to Hold Centered Clutch Plate

I tightened the nuts on the long bolts 1/2 turn rotating around each bolt until the diaphragm spring was compressed enough to thread three of the clutch bolts in the other holes.  I tightened the three clutch bolts until they had bottomed and removed the long bolts.

New Clutch Bolts and Long Bolts

New Clutch Bolts Inserted and Long Bolts Ready to be Removed.

I slide the transmission back into the clutch plate splines to be sure the tabs on either side of the transmission clear the engine case. I was pretty close but not perfect. I used a rubber mallet to tap the transmission on the side with the tab touching the engine case to center the transmission so it can slide into the engine completely.

Transmission Alignment Tab

Transmission Alignment Tab Has to be on the Inside of the Engine Housing on Both Sides

I threaded in the other three clutch bolts and snugged them up. I hung the metal bar on the top left transmission mounting bolt and put it inside the engine housing and against one of the ribs in the compression plate. The old style compression plate does not have ribs so the bar can contact a clutch bolt to stop the crankshaft from spinning as the clutch bolts are torqued. But the new compression plate ribs are exactly as high as the clutch bolt head, so this doesn’t work. I kept the bar against the rib with one hand while I torqued the bolts with the other to 17 FOOT/pounds. I had to rotate the engine a bit so none of the clutch bolts were obstructed by the bar.

Metal Bar Wedging Compression Plate Prior to Torquing Clutch Bolts

Metal Bar Wedging Compression Plate Prior to Torquing Clutch Bolts

I remounted the transmission on the clutch splines to be sure it was square with the engine and would go all the way back to the engine clutch housing.

Transmission Aligned with Engine

Transmission Aligned and Tight to the Engine Clutch Housing

Transmission Aligned with Engine

Transmission Aligned and Tight to the Engine Clutch Housing

When I get the engine in the frame, I’ll put the clutch actuator rod into the transmission and mount it to the engine, but for now, I’m done.

4 thoughts on “21 BMW R75/5 Install New Clutch

  1. Pingback: 1973 R75/5 Rebuild: Installing a New Clutch | Motorcycles & Other Musings

  2. Genius – using the transmission itself to center the clutch friction plate. Didn’t necessarily want to spring for the clutch alignment tool, and the other method I’d been told of (by a highly thought of airhead guru) is to wrap electrical tape around the clutch rod ’til it fits snugly in the clutch plate, then use a square to line it up. Liking your method SO much better than either of the others. Thanks!

    • Hi Charlie,

      This technique seemed to work just fine. It takes a couple tries to turn the shaft just enough so the splines can engage, and then everything slides together.

      Thanks for dropping by.

      Best.
      Brook

  3. Actually, I’ve been scanning this trove of /5 resource for awhile now. You’ve got the whole bike laid out pretty well here, I must say a better job of putting it all together than some of the Grand Poobahs of All Things Airhead, who’s wealth of knowledge I respect mightily, but organizational skills – ehh, not so much.

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