Clutch
Pushrod, throwout bearing, lever at rear of transmission, cables, clutch carrier/flywheel, bolts, crankshaft end play, etc.
(INCLUDES ADJUSTMENT of the clutch levers; and crankshaft end play spacers)

© Copyright, 2012, R. Fleischer
clutch.htm
Article 60, subsection 9

>>>>>>>>>>REFER to article on INPUT SPLINES, for additional information!!!<<<<<<<<<<
 

Warning!!.....Warning!!.....Warning!!!
 Under NO circumstances should the flywheel be removed without blocking the crankshaft!
   See article flywheelremovalwarning.htm

You MUST block the crankshaft!!! 
It is true that many have removed and replaced an Airhead flywheel or clutch carrier without blocking the crankshaft, and have had no problems.  My advice, VERY strongly given here, is to take the time to make and use a simple crankshaft blocking tool.   If you do not use some sort of crankshaft blocking tool, and your crankshaft should happen to move forward enough (does not take much pressure nor have to move far at all!) to have one of the thrust washers fall off its pins, you can cause VERY serious damage as you attach the flywheel or clutch carrier. 
 Do NOT chance it!

Since it is a MUST, in MY OPINION, to mechanically block the crankshaft  from moving forward before AND after removing/replacing a flywheel or clutch carrier, you need to know  how to best do that.  This can be done in several ways.  I recommend you do NOT use a towel between the front cover and the alternator rotor, as is sometimes done!!  I recommend a simple and neat method...just make a tool out of a piece of Allen wrench material, and weld a disc (fender washer) on one end, making the length such that the Allen end fits into the alternator bolt, and the disc end presses against the inside of the outer timing chest cover.  Usually 3/4 inch overall.  The length should be such that when some light pressure is applied by the cover, the cover being screwed back towards the engine lightly (but not touching the engine case,
to be sure of having LIGHT pressure).  That is, the tool should be just long enough that the cover can't quite fully fit home all the way.  Obviously you don't want to tighten very much.  A further treatment of how to make this tool is in the TOOLS article on THIS website, item #8.  (that is a hyperlink).   
There is a sketch with information on this website, so you can REALLY see what is going on......SEE, without fail:      flywheelremovalwarning.htm
  >>>>SEE and READ IT!!!<<<<

AGAIN:  See my tools article, about half-way down the page, item #8:  a photo and description of this very simple tool:  CLICK!

That above article on TOOLS also has photos of the clutch assembly tools!

Be sure the OT mark is in the timing window when removing and replacing the flywheel (or clutch carrier).   Do this "removing and replacing" ONLY when the pistons are fully extended outwards.  When the flywheel shows the OT mark in the timing hole, both pistons will automatically be fully extended outward if the flywheel or clutch carrier was already installed properly.  If that is not seen, then the flywheel is mounted to the wrong crankshaft bolt holes.   Many a person has goofed, so, be forewarned!  The flywheel is not  'indexed' and can be installed to the wrong crankshaft holes.  Furthermore, the flywheel is to be centered by moving it back and forth very slightly CW/CCW in its holes, before being fully tightened.

 

Clutch parts, including flywheel, should be identified by marking with paint or punch pricks before you disassemble. BMW did that on some models.  Parts are installed at 120°.   This confuses folks, so pay attention:  In case those marks are not seen, mark your clutch parts (not disc nor diaphragm spring) before disassembly from the 'flywheel' or 'clutch carrier'.  If you see factory marks, those marks are to be oriented so they are, as best possible, 120° apart to all of each other;....NOT lined up!  YOU can make YOUR markings with arrows or single and dual and triple punch marks if you like for the markings TO BE re-lined up later.  

/5 clutches had changes during and after production.   The replacement diaphragm springs were changed, and 6 spacers were no longer used.  
There were several types of diaphragm springs used, and the heavy duty type is usually stamped with the part number.  That part was 21-21-1-234-035.
Some call that the 'sport plate'...but it is the diaphragm spring.  There was a spring common to the R90/6 and R90S, 21-21-1-231-842; it is obsolete, NLA. 
The pressure ring was updated, that is part of the spacer deletion thing, and the new pressure ring is more rugged, and a better heat sink.    If you are
updating, the updated parts are the -035 spring; the 21-21-1-236-332 clutch plate which has an extra set of rivets and a plate, on opposite side, locks those.
Another later part to use is the 21-21-1-231-666 pressure ring.   The early pressure ring had standard blade screws which should not be used; instead use
6 point head Allen screws, and torque to a target of 16.6 footpounds.

BMW made a big change to the clutch/flywheel parts in 1980-1981.  The flywheel as such was dropped, and a lighter 'clutch carrier' was incorporated.   The
throwout bearing was also changed in design.  These clutch parts are very different from earlier models.  The new clutch assembly was lighter, and also
required much less lever force at the handlebars, so shifting was easier; but engine vibration generally increased.   The 1981  ONLY clutch parts (as
opposed to later clutch parts) were sometimes very troublesome, and some nasty failures were seen now and then.   
My comments here do not necessarily apply to the R65:
The initial clutch friction disc, called officially the clutch plate, was 21-21-1-242-370.  A stronger disc, under part number 21-21-1-451-512 was then
used.   The carrier, officially the clutch housing (or, clutch case), was 21-21-1-242-372; it was also beefed up, becoming 21-21-1-451-511, and then
that became 21-21-1-338-722.     Note that during early production of the 1981 bikes, some bikes had factory installed washers between
the carrier and the cover.  They are NOT to be used on replacing these parts.  The early carriers had 6 'ears'; later ones went full circle....so
did not twist and distort nearly as much.   The 1981-1984 diaphragm spring was 21-21-1-242-353, and a higher pressure one IS available,
as 21-21-1-338-508.   There were other updates.  The pressure plate 21-21-1-242-354 became 21-21-1-243-009, which became 21-21-2-302-200. 
The rearmost part, called a case lid or housing cover, was 21-21-242-355; and became 21-21-1-457-280.   Bolts 21-21-1-242-371 became
21-21-1-338-680.   If you are overhauling a 1981 model with original parts, it is a VERY good idea to replace all the parts that were updated
...which is nearly everything!

Disassembling the clutch:
It is important to unfasten the bolts evenly, in a criss-cross fashion.  On the early clutches, those bolts are NOT long enough to do this due to the HIGH diaphragm spring pressure on those models.  So, how to do it?  You remove three of the six.
In place of those three, you install some long bolts and spacers ...from the hardware store....unless you have the BMW factory type clutch tools.   You can then undo those long bolts, evenly, in a criss-cross pattern, bit by bit, until all pressure is off the clutch.   3 of them will do, but 4 is nice.  You will use these same bolts and spacers when RE-assembling.
I reuse the early bolts.  On the 1981+ clutches, I usually use new bolts.
Here is a photo of the factory-type tools for the early clutch (including the centering tool): ClutchFlywheelTools.jpg 

Note that late production discs have no asbestos, and may not grip quite as well, and if you replace just a disc, if the mating parts are worn
 some, they may well not be dead flat, and the clutch may slip...although if used gently, the clutch may break-in after a few hundred miles
 and be OK.    Professional mechanics usually do a clutch job by replacing the three parts, but you CAN just replace the disc, but I would
recommend checking the taper/flatness of the parts.  Use of new parts will guarantee a proper strong clutch, but the set of parts is
 not cheap.   The heavy duty higher pressure spring is a good idea, especially with these later non-asbestos discs on the early clutches.

A SI was issued with a lot more information on where to grease the mating clutch parts....ETC.   That is in the 1992 service fiche, page 4, G13/H13/I13. 
 Basically, it is the contact points of the diaphragm spring.  I use a moly grease there, very sparingly.

HINTs!!!.....exceptionally stiff clutch action can be due to worn, grungy and even broken parts in the clutch throwout bearing area,
including the bearing, piston, etc.    Do NOT forget to change the clutch cable if bad;...it can FEEL OK with the cable disconnected at the
transmission end, yet be very stiff when in actual operation.   Do NOT have the clutch cable running with sharp bends; nor more than the
ONE tie on the right down-tube.  Be SURE to grease the bar lever area (not the pivot there, it is nylon lined), and be SURE that the cable
 inner strands are NOT fouled by the slot in the bar lever as you pull the lever back towards the bars. Wiggle the lever UP AND DOWN TOO,
 to see if there is so much play in the lever bushing (nylon and replaceable) that strands foul in the lever slot.   It is especially important
 that the cable end, called a cable barrel, be free to rotate in the clutch lever.   Pulling the clutch lever slowly backwards will show if the
barrel is moving freely.  If not, unfasten the cable from the lever, and clean up any rough spots on the barrel, then reinstall using a moly
 grease on the barrel.   The lever at the bars pivots on the screw/pin, via a plastic (Nylon probably) bushing in the LEVER.  If the lever has
too much free-play, replace that nylon-like bushing.  Failure to do so might allow the lever to foul, in the lever slot, the cable strands....and
 the cable will snap eventually.  Mind my caution on lubing the barrel.  I use a moly grease.
NOTE!....BMW has shipped brand-new cables wherein the barrels do NOT rotate smoothly.  Do some hand-filing!

Grabby clutches can come from many things, including excessive crankshaft or transmission input shaft end play.

Throwout bearing, etc:

Slipping clutch?  Acts up when engine fully heated up?...etc...??

This problem has been reported now and then with motorcycles as late as the early 1990's manufacture!

On 1980/1981 and later models, the plastic 'piston' with the metal center, that the clutch lever at the back of the transmission applies its force to, might be too large in diameter, and stick in the transmission bore when hot.  This throwout piston part is next to the 1 inch mark of the ruler in the photo below.     The LIMIT is 28.7 mm, and it can be sanded down, or replaced.  This occurred because tolerances on some transmissions throw-out area bore sizes, and these throw-out pistons were not held tight enough.  If the piston fits into the bore a bit too tightly ....(it may still operate fine when cold), under some circumstances, PARTICULARLY when HOT, the piston may stick.  That is because that plastic piston material expands a lot faster than the aluminum bore it fits into.  Obviously this means that a proper check is with a hot transmission!    This can manifest itself in several ways, INcluding a slipping clutch.   Measure the piston, and if it is over about 1.13" (28.7 mm) when hot, you MAY want to reduce the outside diameter a bit.  I have seen these as large as about 1.142" that still worked OK (NOT all at that diameter WILL be OK!!).  I can't give a hard and fast rule here, but if yours is up to 1.141 or so, I would certainly see how it fits, and if a bit too much friction with a HOT PISTON, I would recommend sanding the OD a bit.  You might want to check the fit, hot, if you have any hot clutch slipping problems, but OK when cold.   Whilst this modification can be done on a lathe with some sanding paper, you can also chuck the rather short shaft tip end in a drill press and use some rather fine sandpaper for this.   Use a micrometer or vernier caliper to measure the piston diameter.   Inspect the bearing, and if it looks bad, replace it.  Grease it with a good grease (Do NOT use moly).    While the bearing is theoretically lubricated by oil from the transmission, that is not hardly so at initial assembly....so use a soft mild grease, non-moly.

>>>BMW has had several versions of the unit, and offers a replacement piston:  23-13-1-464-167, another way of coping with a sticky hot piston....and if your
 old bearing is shot, and piston sticking when hot.....you could consider this pricey part, as it is a new design, and incorporates the bearing, and it has the proper diameter.  If your old items are in good condition, you really do NOT have to spend the bucks....you can sand your piston outside diameter.  It has been reported to me that BMW MAY have recently shipped all-plastic parts that have the same old problems!....so, be sure that no matter what part you have in YOUR bike, that it is not expanding and seizing up!...measure the part!  
 

NOTE:   From 1970-9/1980, the 4 speed transmission had a ball bearing throwout bearing; the 5 speed transmission (1974+) had a radial needle bearing type.
             From 9/1980 BMW went back to the superior ball bearing, of a new design.
NOTE:   The 4 speed transmission and the early 5 speed transmission clutch push rods had felts located in a groove, and are installed best from the front.

Below is a picture of a 1982 felt-less model clutch rod, ball bearing, piston with plastic outer, the internal spring, a new rubber accordion cup, and the
 band-clamp.  The rod is about 9 inches long; the piston cup is about 17/32" wide on the DARK plastic portion.

NOTE!.....the bearing is lubricated with transmission oil during operation; but that takes time and miles...so....  I always use a very light
NON-moly grease when installing this bearing.  NOTE ALSO that the "felt-less' clutch rods came into being in 1981.  Prior models of clutch rod
 had a felt, 23-21-1-230-440, which is best installed on the rod, and the rod inserted from the FRONT of the transmission.  It is possible from the
rear, with a homemade tool, but I recommend against it.  

The felt IS necessary on models prior to 1981, otherwise the clutch disc can become oiled and thereby slip, and be ruined eventually. 

The 1981 and later models have a lipped seal, not easily replaced....the transmission must come apart.

  WARNING!

Earliest models, the /5 that is, had the clutch actuating arm at the rear of the transmission held to the transmission, via a cotter key.  Very reliable. 
The later but still early models had the clutch actuating lever at the rear of the transmission held to the two bosses of the transmission cover by a PIN, that
used a single C clip.  That C-clip fit on the pin at the INside of the lower boss.  If the clip came loose, the pin could come upwards, and come out of the
lower boss, and the next clutch application could, and often did, break off a transmission boss ear...necessitating a transmission overhaul....or some
inert gas welding at a minimum.  
 

A cure is to remove the old pin and clip and install the following parts:
#23-13-1-241-484  pin, that has a flange, and won't fly out.   This is used with a clip that is part number  51-23-1-864-963. 
 

_{Another HINT!.....
     BMW Service Information bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, and this can also be seen on
 the 12/92 fiche on page 3, G23::    Basically, it stated that while the flywheel bolts were previously at ~75 foot-pounds (100 Nm), they
were now to be at 90 foot-pounds (125 Nm), cleaned threads, and then the threads were to be OILED!  BMW specifically said that the
bolt limits would NOT reach their limit of elasticity at that torque, and could be REUSED!    I will NOT tighten them that tight.  Makes me
very nervous!  However, some do tighten them that tight, and I have heard of no problems reported.  It is YOUR CHOICE.  NOTE also
 that this is in regards to the 11 mm bolts, and applies to 1981+ models....certainly not the smaller /5 and early /6  10 mm bolts; which
 need replacement upon each use, which the 11 mm do not, and those 10 mm bolts in the /5 and early /6, are absolutely not be torqued
 to such high values.   There have been a lot of different specifications on flywheel bolts over the years.    There were two lengths of
10 mm bolts used.  I use, clean and dry, torques of 42-45 foot-pounds on the 1973 and earlier engines; and for the 1974 I use 52-55 ftlbs;
 and 1975 and later up to the 1981 models, I use about 75 to 80 ftlbs.  I use about 80 ftlbs, clean and dry threads, on 1981+.}

_{Grabby clutch:   If your clutch is grabby, it can be due to a number of causes.  It is IMPORTANT that the transmission input shaft splines
 be regularly lubricated.  When they get dry, clutch action is poor, and shifting can be stiff and poor.   Never lube the disc spline, just the
transmission INPUT spline.   Cleaning and re-lubrication should be done at a mileage and time commensurate with your driving habits
and atmospheric conditions.   Moisture condenses on the shaft and with the in-out movement during operation of the clutch, and the
wiping action of the essentially gear-like teeth under torque, all conspire to move the grease out of the splines.   Late splines were
nickel-plated, and hold up a bit better and longer, regarding lubrication.  Spline wear, if not lubricated, can lead to spline failure, a $$$
situation; especially so on pre-nickel plated ones.   I suggest a look-see and cleaning and lubrication of the splines at 15,000 miles since
last cleaning and lubrication, and then adjust the mileage for the next following time.   NOTE that end play of the input shaft can cause a
 quite-grabby clutch operation, and that can happen cold and/or hot.  More often when hot.  To fix THAT, one must remove and open the
transmission and work on the shaft shimming.  One can get an idea if that is a problem by removing the transmission, heating it to about
 the temperature of boiling water, and measuring, with a dial indicator, the input shaft end play.  Anything over a few thousandths of an
 inch is suspect.  This problem with transmissions causing a grabby clutch is not overly common, but it seems to be more so for the 1979 models.}

EZ-Clutch (and variations):  The pre-1981 clutches have a heavier pull at the bars, some dislike that, or cannot easily physically cope with it.  There are several types of modifications to fix it, besides the HUGE expense of installing a 1981+ clutch.   Modifications involve a single pulley device or a lever arrangement.  One that is available for purchase is from Craig Vechorik ('Vetch'), dba Bench Mark Works.  (662) 465-6444; located in the USA;   www.benchmarkworks.com/articles/howto/clutch.html   They also have it available from a place in Canada.     There is also a type you could build, that has some advantages over Craig's...as the original cable end can be used.   Here is a website with photos to give you some ideas:  http://www.frankhams.freeserve.co.uk/temporary_uploads/ezclutch_page.htm
There is another type, can't remember the URL for the website.
 

There is a factory tool to help line up the disc when assembling the clutch to the flywheel/carrier.  You don't have to have one, eyeball is good enough.  If you
want to make this tool:  

The tool, overall, is roughly 133 mm long. Starting at the taper tip:   The non-tapered portion of the tip is 8.2 mm diameter and 5 mm long.  The taper is a simple
 rounding, or, just do a 90° tip....not sharp though.  So, with taper, the tip is a tad longer than 5mm...maybe 8 or 10 or whatever.  Back of the tip is the second
 section:   29 mm long by 20.7 mm in diameter. The 'handle' portion is 95 mm long and 22 mm in diameter.

Here is a photo of the factory-type tools for the clutch: ClutchFlywheelTools.jpg

Here is a hyperlink to my tools article:  TOOLS.htm    In that article will be found information on clutch removal and assembly tools

Assembling the clutch: 

Here is a hyperlink to my tools article:  TOOLS.htm    In that article will be found information on clutch removal and assembly tools

Unless the clutch parts are pretty flat, you need to contact such as Southland Clutch to machine your plate and make you a thicker disc to compensate for that machining; or, you need to purchase new parts.  Many folks just replace the disc, and have to do a clutch job all over again, soon enough. 

During your assembly (don't forget previous information on marking the parts and 120° assembly), I suggest you coat the edge of the diaphragm spring where it touches the flywheel and the fingertips with thick moly grease/paste....not very much!  This will help the spring fit properly and operate smoothly.  Remember:  just a tiny coating.

Torque, evenly, the clutch bolts.   You will need some sort of long bolts and some spacers from the hardware store (unless you have the BMW tools), in order to get the pre-1981 clutch to assemble to the point you can use its original bolts. You don't need more than 4 of these long bolts...three will do, as the clutch has 6 normal bolts, and three can be spread at an even 120°...you will also need some spacers for them.   You install these long bolts evenly, criss-crossing while tightening them evenly, bit by bit, until the clutch is pulled together, only moderately.  THEN you can install the original bolts, and torque them properly....one by one.  For the 1981+ clutch, replace the clutch bolts.

Flywheels, clutches, and their bolts: 

1981 and later bikes used Clutch Carriers, NOT officially called flywheels.

 
HINT!.....The early R65 and R45 had smaller clutches than the larger engines did.  The 1989 and 1980 had 6 x 1.00 mm CLUTCH bolts. 
The amount to torque the clutch bolts to the flywheel is NOT listed in early BMW literature; and is wrong in some later literature.   There
is some confusion over this.  BMW originally had Allen head bolts, then later went to hex head bolts.  I suggest using the hex head bolts. 
Some published figures are as high as 17 foot-pounds for the clutch bolts (any style).  That is WAY too high, even for high strength bolts.
 I suggest 88 inch-pounds (7-1/2 foot-pounds),  for the 1979-1980; and, use clean, dry threads, then coat before assembly with a light
amount of Loctite BLUE.   It is possible that up to 10 foot-pounds is OK, but that would be for high grade bolts only.   Any book figures you see that say 17 foot-pounds,
or 15 foot-pounds, is WRONG!

 All 11 mm bolts up through PRE-clutch carrier models (came out in 1981):   The original good specification was:   Torque these to 73 ftlbs.   
Threads were to be clean, dry, NO Loctite used.   

Repeating!:

     _{BMW Service Information bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, and this can also be seen on the
 12/92 fiche on page 3, G23::    Basically, it stated that while the flywheel bolts were previously at ~75 foot-pounds (100 Nm), they were
now to be at 90 foot-pounds (125 Nm), cleaned threads, and then the threads were to be OILED!  BMW specifically said that the bolt
 limits would NOT reach their limit of elasticity at that torque, and could be REUSED!    I will NOT tighten them that tight.  Makes me
very nervous!  However, some do, and I have heard of no problems reported.  It is YOUR CHOICE.  NOTE also that this is in regards
 to the 11 mm bolts, and applies to 1981+ models....certainly not the smaller /5 and early /6  10 mm bolts; which need replacement upon
 each use, which the 11 mm do not, and those 10 mm bolts in the /5 and early /6, are absolutely not be torqued to such high values.  
There have been a lot of different specifications on flywheel bolts over the years.    There were two lengths of 10 mm bolts used.  I use,
clean and dry, torques of 42-45 foot-pounds on the 1973 and earlier engines; and for the 1974 I use 52-55 ftlbs; and 1975 and later up
 to the 1981 models, I use about 75 to 80 ftlbs.  I use about 80 ftlbs, clean and dry threads, on 1981+.}

Cables: 
32-73-2-324-956 cable is 1460 or 1495 mm long and the sheath is 1285 mm long.  This cable may have been 32-72-1-235-744???
32-73-2-324-958 cable is 1385 mm long, and the sheath portion is 1155 mm long
32-73-2-324-959 cable was used on R65 Euro, 86+RS   is 1386 mm long
32-73-1-230-041 cable is 1320 mm long, and the sheath portion is 1085 mm long
32-73-1-230-042 cable is 1460 mm long, and the sheath portion is 1225 mm long
3273959 is 1361 mm long, sheath is 1130.  Needs confirmation.  Believe was on R45/R65
3273694 is 1469 with 1242 sheath, needs confirmation, believe was used on R45/R65 with high bars.
32-73-2-324-960 is 1625 mm and is on K1100LT
3273957 is 1410 long, sheath 1180, used on R80, R100, Mystic

See www.siebenrock.com for more control cable information

Southland Clutch; 101 E. 18th St., National City, CA, 91950, (619) 477-2105, can resurface all models of Airhead worn clutch parts and supply the thicker
 clutch disc that is needed after those operations.  Dan Levine.   Dan@southlandclutch.com

 

Clutch Adjustment:
The way I look at the adjustments is to first be sure cable is routed properly, and then tied down only once at the frame.  That tie, which must be only moderately tight,
 should be located roughly midway down the right side frame down-tube.  There must be no broken cable strands.  The clutch lever at the bars should not have excessive
UP and DOWN play, and if it does, the nylon bushing IN THE LEVER needs replacing.  BE SURE that with lever movement in any direction the inner cable strands are
NOT being rubbed against by the clutch lever slot.  Be SURE the barrel rotates easily... lubricate the barrel and the transmission ends with moly grease.  I inspect quite
carefully the clutch lever at the bars.  The nylon insert in the lever wears, and the lever gets sloppy, and once things are sloppy enough, the cable core strands can foul
on the lever slot.   Is even worse if the barrel on the core wires is not rotating in the lever.  Lube the barrel and lever  (the nylon bushing does not need lubricant), and make
sure that if the lever is moved UP and DOWN, the cable does NOT foul the lever slot....and that the barrel DOES rotate.  Smooth the barrel metal if it fails to turn properly,
check its fit in the lever.   Some replacement cable barrels do not fit smoothly...fix that!  Failure to ensure that the lever, barrel, etc., are OK, could destroy the cable quickly.
  Replace the nylon bushing if it is allowing too much slop in the bars lever, an easy job.  These little things can greatly extend cable life.

Rev:
01/26/2008:  all prior revisions incorporated, and much added from old obsolete engineinternals.htm
05/04/2008:  Edit section on the plastic throwout bearing piston problems.
04/16/2009:  Clarify a few details.  Re-arrange order of presentation of items.
10/27/2009:  Clarify a few things, fix and add hyperlinks.
11/04/2009:  A few additional clarifications on R65/R45 clutch bolts; and re-arrange article somewhat, it was excessively gaudy.
06/24/2010:  Clean up article some
04/29/2011:  Add more information, such as a link to the factory clutch tools picture on this site, etc.  NO errors found.  Strictly a clarification revision.
06/16/2011:  Add Stuck Clutch section, minor other clarifications, quite minor
09/08/2011:  Fix typo in part number for the early eighties heavy-duty diaphragm spring; was 2121338508, should be 21211338508.
10/02/2011:  minor clarifications (which I forgot to upload for months)
03/28/2012:  add note and hyperlink to my tools article.
04/08/2012:  Very minor clarifications on throw-out bearings.

© Copyright, 2012, R. Fleischer

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