Sticking Clutch repair on a BMW R60/2

An R60/2 meandered into my shop with a sticking clutch.  In other words the clutch wouldn’t release properly. When idling and standing still, and the clutch lever squeezed, the bike was difficult to shift into 1st or 2nd.  Once in gear and the clutch lever still squeezed, the bike shuddered and clanked, as if the clutch was not releasing fully, which is was obviously not.

I started by adjusting the clutch to determine if the problem was a clutch out of adjustment. Proper adjustment of the clutch is when there is about 1/2″ of free play at the lever.

This didn’t help.

I also removed the throwout bearing to see what it looked like.  It looked fine.

So I began to remove the tranny to have a look at the clutch.

 

First, I peeled back the prop shaft boot to discover that the tranny case was cracked. This appeared to be an old wound that was most likely caused by the prop shaft bolts getting loose and the u-joint coming loose during driving. Not good at all.  I would like to repair this with the TIG, but it is not in the owner’s current budget.  Well, it does not appear to be leaking and isn’t impeding operation of the u-joint. Maybe we’ll fix it up later.

Next, I removed the bolts.

 

My technique for loosening the prop shaft bolts is to put my right knee on the rear brake to keep the prop shaft from spinning.

Not shown: I remove the upper motor mount bolt, just the single horizontal bolt with the split pin in it. No need to unbolt the two 14mm bolts on the top of the case.  Next, loosen both lower motor mount bolts.  Remove the rear mount bolt entirely (along with both foot pegs, noting the position of the pegs with some white-out).

Disconnect the electrical ground on the back of the tranny, along with the Neutral Indicator wire. Tape them out of the way.

Now position a jack under the rear of the oil pan with a block of wood to protect the pan and begin to jack up the back of the motor.  Be mindful that you don’t scratch the horn.

 

 

 

The transmission is easy to remove at this point. Remove all four bolts and slide the tranny back and out the left side of the bike.

Use an impact driver to loosen the flat head clutch screws.  Don’t try this with a regular screw driver; you’ll just wreck the screw heads.  Begin by removing two of the screws opposite each other.

 

Insert the clutch removal tools.  Some people use three. I find that two works fine.

Now that you have the tools in place, remove the remaining clutch screws. When all screws are out, loosen the thumbwheels on the tools to release the clutch spring tension.

Now that the clutch is removed, let’s have a look.

 

A sticking clutch is normally caused by one of two things. Either the clutch push rod is worn so much that it can’t disengage the clutch sufficiently, or there is dust built up inside the clutch housing which impedes the operation of the clutch.  Only one of the clutch versions which emerged from BMW is  susceptible to this because it is a sealed design. Some other designs from BMW were designed with gaps to permit the dust to escape. Duane has a wonderful page on his site which discusses the different clutch versions.

The friction disc is worn.

 

This does not surprise me because once the clutch begins dragging it wears faster and faster because the dust acts like a grinding compound. Eventually the clutch won’t release at all.

Copious quantities of clutch dust inside the clutch:

 

Unfortunately, on this bike, the problem was left long enough to damage the clutch faces. They will need to be replaced.

 

Check out how much dust fell out of the clutch when I opened it.

 

After cleaning the bell housing and transmission face with cleaner, I greased the transmission input shaft spines with Honda Moly 60.  I only grease the input shaft splines, not the flywheel hole. This keeps extra grease from flying about.

I also took a few moments to inspect the clutch push rod.  Check out Duane’s page to see how these wear down and what to do about it. The one on this bike looked good, so I just cleaned it  and the throwout bearing in the parts washer, greased it up and re-installed.  Put a small dab of Moly 60 on the cup where the push rod meets the clutch plate.

I happened to have a complete used clutch in stock, which I used to keep the repair costs down for this customer. The clutch went back together and is working good now.

Murphy’s Law repairs: The exhaust ports on the heads are known problems on /2.  The aluminum threads oxidize and turn into dust. This makes it impossible to tighten the collar nut on the exhaust header.  A common fix for this is to TIG weld new aluminum on to the head and machine new threads.

On this bike, apparently, someone had tried to repair the threads in an unconventional fashion.  It looks like they machined off the threads from the head’s exhaust port.

 

When I was attempting to loosen the collar nut, the set screws holding the sleeve sheared (you can see them in the above photo).

Now the sleeve is stuck inside the collar nut.

Kind of messy.

I suppose I have two options to repair this.

1)  Use a cut off wheel to slice open the collar and salvage the previous repair sleeve.  Then extract the broken set screws and repair the repair.  In this case, I’ll need to get a new (or used) right hand header pipe because the collar nut is captive on the header pipe.

2) Remove both heads and have them both repaired “properly” by TIG welding new threads on.

I need to find out what the customer wants to do.

 

The rest of the exhaust system has seen better days, so maybe the customer will want to spring for a complete new exhaust.

We shall see!

 

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