Adjustment of clutch levers and fixing potential breakage problems of cables.
Lubrication of clutch splines (input splines of transmission).
Preventing broken ears at transmission clutch lever.
Clutch carrier/flywheel, bolts, crankshaft end play.
Cables...and problems with brand-new ones.
Throw-out bearing & pushrod.
Crankshaft end play spacers.
1981 Clutch/carrier problems.
Copyright, 2014, R. Fleischer
Article 60, subsection 9
Under NO circumstances should the flywheel or clutch carrier, on ANY models
be removed without FIRST blocking the crankshaft!
You MUST block the crankshaft!!! DO NOT TAKE A CHANCE!
Many HAVE removed & replaced an Airhead flywheel or clutch carrier without
blocking the crankshaft & had no problems. My advice, VERY strongly given here,
is to take the minor amount of time to make & use at least my simple crankshaft
blocking tool. If you do not use some sort of crankshaft blocking tool, & your
crankshaft should happen to move forward enough (does not take much pressure
nor have to move far!) to have one or both of the thrust washers fall off their pins,
you can cause VERY serious damage as you attach & bolt-up the flywheel or
clutch carrier. At a minimum, if the forward thrust washer drops, you may be
UNABLE to get it back on its pins without a LOT of work. Do NOT take a chance!
Since it is a MUST, in MY OPINION, to mechanically block the crankshaft from moving
forward at any time during the process of removing/replacing a flywheel (or clutch carrier as
it is called on 1981+ including some 1980 models), 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 & the alternator rotor, as is sometimes done. I recommend a simple & neat method...
just make a tool out of a piece of Allen wrench material, weld a disc (fender washer) on one
end, making the length such that the Allen end fits into the alternator bolt, & the disc end
presses against the inside of the outer timing chest cover. Usually 3/4 inch overall. The
length should be such that there WILL BE some light pressure applied by the cover to the
tool, the cover being screwed back towards the engine lightly (but not touching the engine
case, ...again, LIGHT screws pressure). The tool should be just long enough that the cover
CAN NOT fit fully home all the way. Obviously you don't want to tighten very much & DO
NOT NEED TO! A further treatment of how to make this tool, & a photo of it, is in the
http://bmwmotorcycletech.info/tools.htm article on THIS website, item #8. Note that
making the tool requires a very small amount of welding. If you do not have a welder, or
do not wish to have the tool made that way, you can just use a piece of allen wrench, OR,
simply remove the rotor bolt & use a common bolt temporarily at the rotor, adjusting its
depth to fit the outer cover. That above tools article also has photos of the clutch
disassembly & assembly tools...you may need one or more if you have an early model.
There is another place on this website with a photo, etc.,
of that tool. I suggest you go look at that article, NOW:
>>>>SEE and READ IT!!!<<<<
Be sure the OT mark is in the timing window when removing & replacing the
flywheel (or clutch carrier). Do this "removing & 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' & can
be installed to the wrong crankshaft holes. The flywheel is also to be centered
in the proper selected holes, by moving it back & forth very slightly CW-CCW
in its holes, before being fully tightened. It may be moveable a TINY amount if
the bolts are a fraction of a turn loose...so find the centering position, then
tighten carefully, & then torque to specifications.
Clutch parts, including flywheel or carrier, should be identified by marking
with paint or punch pricks before you disassemble. BMW did that on some
models. Parts are installed at 120° with respect to the BMW marks, which may
exist & may not. This is contrary to what the repair industry usually does, which
is to align marks. I use one punch prick opposite another for the first marking;
the next set, if needed, is two punch pricks, then three, etc. Arrows also work.
Those are standard methods. I don't use paint or other marking methods.
If you see factory marks, those marks are to be oriented so they are, as best
possible, 120° apart to each other; that is, they are NOT lined up!
/5 clutches had changes during production.
The replacement diaphragm springs
were changed, & the 6 spacers were no longer used.
Spacers are sometimes added if parts have been resurfaced...but that is a whole
special story by itself.
There were several types of diaphragm springs used, & 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
The pressure ring was updated, that is part of the spacer deletion mentioned above,
& the new pressure ring is more rugged, & 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 & 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; torque to a target of 16.6 foot-pounds.
BMW made big changes to the clutch/flywheel parts in the transition period
between 1980-1981. The flywheel as such was dropped, & 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 &
required much less lever force at the handlebars; but engine vibration generally
increased due to the lighter flywheel effect.
The 1981 ONLY clutch parts (as opposed to later clutch parts) were sometimes
very troublesome, & some nasty failures have been seen. My comments here
do not necessarily apply to the R65.
Note that there were some soft splines
on these clutch discs, which can cause failure of transmission input
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. During early production of the 1981 bikes,
The 1981-1984 diaphragm spring was 21-21-1-242-353, & a higher pressure
version IS available, 21-21-1-338-508 (which I recommend). 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; & 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!
Clutch friction discs were asbestos in the old days, which had, I THINK, a
better Coefficient of Friction, than today's replacement discs; probably
another good reason to use a sport diaphragm.
New discs are ~6 mm thick. When worn below the official limit, 4.5 mm, they
may slip. Slipping tends to show up first when using large amounts of power
in top gear. If the rest of the clutch parts are in reasonable condition
slippage may not occur until ~3.5 mm. No hard & fast rule here, due to wear
(cupping on the pressure plate, wear on the diaphragm, friction material, etc.
I check clutch parts on a machinist's flat, but you can use a flat piece of glass,
etc. You can use feeler gauges to determine the dishing, etc. Check disc
thickness via vernier caliper or micrometer. Another way, very commonly
done to determine if the parts besides the friction disc may need resurfacing
or replacement, is to measure the width of the worn disc of the friction
material (both sides together), near the outside edge, & re-measure near the
center. If the thickness is considerably different, then all the friction parts
of the clutch need attention. While there is no directly official specification,
you could determine it from how BMW shows the various distances, etc....
and find that to be ~0.3mm...disregard that, and use my ~0.5 mm. Check the
diaphragm spring with vernier for height, etc. See the specifications in the
various literature. The diaphragm spring has specifications, vary with
model as to height & as-fitted pressure & when pressed flat. There is also
a specification for the height differences of the spring fingers. Ask about
these on the Airheads LIST. I suggest that only the un-pressured height
usually needs be checked (besides inspecting for unusual wear).
If you replace just a friction disc & the mating parts are worn enough
(especially if they are not flat or flat enough) the clutch may slip...although
if used gently, the clutch may break-in after a few hundred miles & then be
OK. Using gently here means not letting the clutch slip hardly, which will
happen if you use high throttle and top gear until broken-in. 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. The heavy duty higher pressure spring is a good idea,
especially with these later non-asbestos discs on the early clutches.
Clutch PARTS can be overhauled. Southland Clutch modifies old parts
& supplies a thicker disc (as needed with their machining of the originals,
etc. http://bmwmotorcycletech.info/references.htm under C for clutch....or,
see much later in this article, below, for their information.
Disassembling the clutch:
It is important to unfasten the bolts evenly, in a criss-cross fashion on the
clutches prior to 1981, this means all the clutches that are NOT the later
Clutch Carrier type. On these early clutches, those bolts are NOT long enough
to do this without a spring-loaded problem from the clutch. So, how to do it?
You remove three (alternately spaced) of the six. In place of those three, you
then install three longer bolts & spacers ...from the hardware store....unless
you have the BMW factory-type clutch tools; or, tools from some aftermarket
maker. With either the hardware store bolt method or the factory/etc., tools,
you can then undo the other bolts, evenly, in a criss-cross pattern, bit by bit.
I reuse the early models bolts (I inspect them of course).
On the 1981+ clutches, you will be using new bolts. Use NEW special
vibration-proof washers too! On the 1981+ clutches, there is NO need for the
above release method, simply remove the bolts. Note that these clutches can
stick from corrosion at the bolting areas. Use a small flat blade tool, even a
screwdriver; gently pry a bit here, a bit there, & over a few minutes the clutch
will come apart. Here is a photo of the factory-type tools for the early clutch
(including the centering tool):
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 a BAD CABLE; or,
worn, grungy or failing bearing & even broken parts in the clutch throwout
bearing area, including the bearing, piston, etc. Do NOT fail 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 install
the clutch cable running with sharp bends; nor have more than the ONE tie
on the right down-tube. Be SURE to grease the bar lever clutch cable
barrel-end & barrel itself area (moly!). 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 or move the lever up and down. Yes, that means to ALSO wiggle the
lever angularly UP AND DOWN, to see if there is so much play in the lever
bushing (nylon & replaceable) that some strands foul in the lever slot. It is
especially important that the cable end, including its cable barrel, be free to
rotate in the clutch lever. The crimped area at the barrel end must not foul
the lever either, & you might have to file that a bit. Pulling the clutch lever
slowly backwards will show by #1 eyeball if the barrel is moving freely. If not,
unfasten the cable from the lever, & clean up any rough spots on the barrel,
then re-reinstall, again using a moly grease on the barrel. If the nylon
bushing needs replacement, do so. If it does not fit properly, then ream it
SLIGHTLY. There is a waverly washer used in a machined depression in the
clutch lever, it must be there. Some clutch cables are poorly made. The
curved area for the barrel in the transmission lever may need filing to
enlarge the curve very slightly, so the barrel will easily rotate.
More on that in next paragraph.
More information on cables and levers, etc:
Clutch cables...and transmission lever (more):
BMW clutch cables (since just after the earliest /5 bikes as originally shipped)
are lined with a plastic material. DO NOT LUBRICATE. BMW has sometimes
shipped POOR QUALITY cable ends, you may have to file the barrels round or
otherwise fix the ends. While I have discussed the barrel on the clutch cable
which fits the handlebar lever, and the curve in the transmission lever for the
clutch cable barrel, here it is in more detail. This problem is due to rough
manufacture of the clutch cable barrel (at the transmission lever end of the
cable); and/or, poor machining of the clutch actuating arm located at the rear
of the transmission. This is an easy ...and lasting...fix.
I always check this area when I am adjusting the clutch & when removing the
transmission for any reason.
1. Inspect the cable barrel. It must be smooth & round. If not, file it so,
finishing with sandpaper.
2. Be sure that this cable barrel can rotate smoothly on the clutch lever fork.
If not, use a fine rattail file & enlarge the opening in the lever, so the
half-round area is a bit bigger. I give a slight bias to the main body of the
lever, rather than the tip. Clean up any sharp edges; & then use fine
sandpaper on any convenient round object, such as a screwdriver shank,
to smooth the area.
3. Clean up the slot with sandpaper, so there are no sharp edges.
4. Using very fine sandpaper, or a fine wire-wheel, polish the rotating area, etc.
5. CHECK how the cable barrel rotates now, in the arm.
If the clutch cable is not properly adjusted, the clutch can slip; shifting can be
bad, the hand pressure can be high....and more...including a worn out throw-out
bearing. The clutch can slip from a thin friction disc, worn parts, & also from
throw-out bearing problems....I discuss that just below.
Throwout bearing, etc:
STIFF or no clutch or slipping...when engine fully heated up (or even when cold)?
This problem originally was reported now and then with motorcycles as late
as the early 1990's manufacture! It is NOW clear that the problem exists, even if
rarely, on the last of the Airheads, such as the R100R, & even with the "new"
throwout bearing that BMW went to. THUS, this section was revised 05/16/2013.
On 1980/1981 & later models, the PLASTIC (which looks like aluminum) or
ALUMINUM 'piston' (yes, both types were made) with the metal center, that the
clutch lever at the back of the transmission applies its force to, might be too large
in diameter & stick in the transmission bore usually when hot. This piston is next
to the 1 inch mark of the ruler in the photo well-below. The LIMIT is 28.7 mm, & it
can be sanded down, or replaced. This occurred because of accumulated error
tolerances on some transmissions throw-out area bore sizes, & these throw-out
pistons themselves. I believe that the plastic ones ALSO MAY age, expanding over
time/miles. If the piston fits into the bore a bit too tightly ....(it may still operate
fine when cold), then, under some circumstances, PARTICULARLY when HOT,
the piston may stick. That is because the plastic piston material expands very
considerably faster than the aluminum bore it fits into. Obviously this means
that the BEST check is with a hot transmission.
The problem can manifest itself in several ways, INcluding a hung-up or very
stiff operating clutch, or a slipping clutch. Measure the piston, & 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!!). It really depends on the transmission bore hole,
but you won't be changing that.
I can't give a hard & fast rule here, but if your throw-out piston is up to 1.141 or
so, I would certainly see how it fits, & if a bit too much friction with a HOT
PISTON, I would recommend sanding the OD a bit; keeping it concentric!!
You might want to check the fit, hot, if you have any hot clutch slipping
problems or any stiffening or hung clutch problems, but OK when cold. There
have been some reports that the plastic piston expansion can happen & then
be more or less permanent; after years of seemingly being OK. I think the
'permanent' expansion, if that happens, is likely to be occurring almost from
brand-new, & that it might take a very long time & many miles, for the
expansion to reach the grabbing-seizing point. NO PROOF OF THAT.
While my described modification can be done on a lathe with some sanding
paper, and in a lathe you can hold onto both ends of the piston; you can also
chuck the rather short shaft tip end in a drill press & use some rather fine
sandpaper for the job; which takes a few minutes. The drill press chuck
won't grab strongly on that short tip, so don't over pressure with sandpaper
...AND....take your time. The sandpaper & throwout unit should be DRY, NOT
lubricated, during the sanding. Use a micrometer or vernier caliper to first
measure the piston diameter, & repeat the measurements as you sand it down.
Use a moderate speed of rotation. I usually just do this, rather than replace
the assembly with the newer type...as there has been problems with the new
type, and it takes me only minutes to sand the original. A shop probably
would not sand the old part, but replace it with the updated part. I am not
convinced the new part is perfect.
Inspect the bearing & if it looks bad, replace it. Grease it with a good thin
petroleum grease (Do NOT use moly). While the bearing is theoretically
ultimately lubricated by oil from the transmission, that does NOT happen
for some miles after initial assembly.
NOTE that these bearings, whether ball type, or needles type, can fail, and
MOST of the time the failure is NOT due to what you might think (although
the bearing will be damaged, if not lubricated, upon installation). The
problem is that the transmission oil had become contaminated by moisture.
Transmission oil is moisture contaminated due to any combination of the
following factors: Short trips. Leaking speedometer cable boot at the right
rear top area. Water hose has forced water into transmission via the hollow
bolt. VERY rarely it comes from water in the bottom of the air cleaner area,
where a 13 mm (head) bolt screws into the transmission. That bolt must
have goop put on threads and under the head. Contrary to old BMW
recommendations, I suggest gooping the bolt threads, even under the bolt
head (washer too), with a LIGHT amount of Permatex NON-PERMANENT
BMW has had several versions of the throw-out parts, & offers a
replacement piston 23-13-1-464-167, which is another way, if somewhat
costly, of coping with a sticky hot piston. If your old bearing is quite bad,
& piston sticking when hot.....you could consider this part, as it is a new
design, incorporating the bearing, & it supposedly has the proper
diameter. If your old items are in good condition, you really do NOT have
to spend the money, ....you can sand your piston outside diameter. It has
been said that there is a special surface coating on the piston, & sanding
or otherwise machining is a bad idea...NOT TRUE...sanding works fine, &
lasts. Just do NOT remove way too much material, or the piston could
cant sideways. It is VERY UNLIKELY you will remove too much material.
NOTE that at least one new-style piston has been reported as expanding &
sticking!!!! I had TWO reports that a new-style piston expanded slightly &
permanently, & gave clutch problems with the transmission being COLD.
I personally have not seen this (yet)....& probably will not, since I have stopped
doing work for others. It has separately been reported to me that BMW MAY
have recently shipped all-plastic parts that have the same old problems!
It was reported in May 2013 that a R100R with original "new type" piston
assembly was seizing, & was repaired by sanding or turning the piston
down on a lathe, slightly. That was the first instance I had heard of this on
a R100R. The R100R was the last version of the Airheads, produced into 1996.
|At this point, I think it appropriate to caution that if your clutch operation becomes faulty in some way after the engine is fully heated-up, that the throwout bearing & piston unit should be checked to see if it fits OK cold; &, again when the engine/transmission is quite hot from a reasonably long ride, perhaps 20 miles.
NOTE that if the clutch is not properly adjusted, usually indicated by no free play, hot or cold, at the bar lever, the throwout bearing will WEAR OUT RAPIDLY. Best clutch operation is had with proper adjustments, at the transmission clutch lever & the bars & is outlined in this article.
The 4 speed transmission had a balls type throw-out bearing; the 5 speed
transmission (1974+) had a radial needle bearing type; in 9/1980 BMW went
back to a ball bearing, of a new design. Can you figure out why a radial needle
bearing is a poor design (but CAN work adequately), as far as pure engineering
is concerned?....think, then read the next paragraph.
(((thinking time...thinking time....1, 2, 3, )))
The radial needle bearing for a throwout bearing in an Airhead is a POOR
design, but works fine most of the time. When RADIAL needle bearings are
pressured (say, by a flat plate) & rotated circularly, the needles try to rotate
at the same speed at BOTH ENDS of each needle....that is, from end to end of each
an individual needle. This is NOT POSSIBLE, if you think about it, in radial use,
so they scrape around....forcing any grease or oil out. BUT, the bearings are
NOT being constantly rotated, only when the clutch is used, & when the
transmission oil hopefully lubricates the bearing. Thus, the bearing does hold
up OK most of the time. See downwards a couple of paragraphs, for exceptions.
If the grease (or transmission oil) is not there, & a little moisture condenses there,
or excessive clutch hold-in times are often used ....and/or combinations of these
things INCLUDING OLD OIL.....the bearing can start to deplete its lubrication,
& actually freeze up. That is more likely for dirt riders who use the clutch to
control speed. When you install the bearing, you lube it with a fine thin grease
(NEVER a moly grease), & that grease will lubricate the bearing until the
transmission oil gets to it enough, & washes that petroleum grease away.
NOTE: The 4 speed transmission & the early 5 speed transmission clutch push
rods had felts located in a pushrod groove, & are best installed from the front.
More to that, below.
As noted, the 4 speed transmission had a balls-type throw-out bearing. The
early 5 speed transmission had a radial needle bearing. From ~1981, BMW BMW
went back to the ball bearing. The radial bearing is, IMO, a poor design; if it fails,
the needles can flat-spot, the bearing can seize, etc. HOWEVER, that is RARE,
& the ball bearing version also can fail, but hardly often. MOST throwout bearing
failures are due to moisture getting into the gearbox!
Below is a picture of a 1982 felt-less
clutch rod, the superior type 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.
The bearing is lubricated with transmission oil during operation;
but that takes
time & miles after the greased throwout bearing is installed. I always use a very
light NON-moly grease when installing this bearing. NOTE ALSO that the
"felt-less' clutch rods came in 1981. Prior models of clutch rod had a felt,
23-21-1-230-440, which is best installed on the rod, & 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; thereby slip, & be ruined eventually.
1981 & later models have a lipped seal at the rear cover, not easily replaced....
the transmission must come apart. Install the pushrod, oiled, FROM THE
REAR, rotating it a bit, to avoid damaging the seal (which you will, if you
install from the front like on earlier transmissions & clutches).
WARNINGS about the clutch arm:
(1) 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. Later,
but still rather early models, had the clutch actuating lever held to the two
tower bosses of the transmission cover by a PIN that used a single clip. That
clip fit on the pin in a groove in the pin, at the INside of the lower tower boss.
If the C-clip came loose, the pin could come upwards out of the lower boss;
the next clutch application often broke off a transmission boss ear...
necessitating a transmission overhaul....or some inert gas welding at a
minimum for a permanent fix (temporary fixes are of several types, not treated
here). Usually the breakage happened while you were shifting, going down
the road; and did not happen in your garage...and the ear was lost...so it now
was more complicated to get back on the road. Replacing a rear cover means
re-shimming the transmission; so you might as well overhaul it.
Fixing the problem before it can happen, which costs VERY LITTLE, can save
you a HUGE amount of money...not to mention headaches, or being stranded:
A PRE-PROBLEM FIX: remove the old pin & clip & install #23-13-1-241-484
pin that has a flange, & won't fly out. This is used with a clip that is part
It is also possible to use a bolt & a self-locking nut; I suggest a shoulder type bolt,
& do NOT try to squeeze together the ears, they will break! Tighten the nut JUST
enough so the bolt has some free-play & is NOT squeezing the transmission cover
LUBRICATE the parts, no matter the type of fix, with moly-grease, during assembly.
(2) Clutch arm and cable barrel problems:
BMW clutch cables (since just after the earliest /5 bikes as originally shipped) are
lined with a plastic material. DO NOT LUBRICATE. BMW has sometimes shipped
POOR QUALITY cable ends, you may have to file the barrels round or otherwise
fix the ends.
While I have discussed in this article the barrel and cable tip swaging on the clutch
cable which fits the handlebar lever, there is another problem due to rough
manufacture of the clutch cable barrel (at the transmission lever end of the cable);
and/or, poor machining of the clutch actuating arm located at the rear of the
transmission. This is an easy ...and lasting...fix.
I always check this when I adjust the clutch & when removing the transmission
for any reason.
a. Inspect the cable barrel. It must be smooth & round. If not, file it so, finishing
b. Be sure that this cable barrel can rotate smoothly on the clutch lever fork.
If not, the fork was not made correctly....an easy fix.
c. Using a fine rattail file, enlarge the opening in the lever, so the half-round
area is a bit bigger. I give a slight bias towards the main body of the lever,
rather than the tip.
d. Clean up any sharp edges & then use fine sandpaper on any convenient
round object, such as a screwdriver shank, to smooth the area.
e. Clean up the slot with sandpaper, so there are no sharp edges.
f. Using very fine sandpaper, or a fine wire-wheel, polish the rotating area, etc.
g. CHECK how the cable barrel rotates now, in the arm.
BMW had a Service Information bulletin (we call them SI's), November 1991,
#11-049-91, sub number 2495, 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, & 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, & I have heard of no problems reported. It is YOUR
CHOICE. NOTE also that this is in regards to the 11 mm bolts, & 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. The 10 mm bolts in the /5
& early /6, are absolutely NOT to 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 & dry, torques of
42-45 foot-pounds on the 1973 & earlier engines; for the 1974 I use 52-55 ftlbs;
for 1975 & later up to the 1981 models, I use about 75 to 80 ftlbs. I use about 80 ftlbs,
clean & dry threads, on 1981+. I am OK with that value even if slightly oily.
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, the shifting is stiff, poor, and may be somewhat difficult to get
from 2nd gear down to first gear, or just to engage 1st. While you could put a
FAINT coating of a DRY type moly on the disc splines, I generally recommend you
do not, as I worry you will over lubricate the disc. So, I usually say: Never lube
the disc spline, just the transmission INPUT spline. Cleaning & re-lubrication
should be done at a mileage & time commensurate with your driving habits &
atmospheric conditions & the condition in which you find the splines during the
servicing. Moisture condenses on the shaft & with the in-out movement during
operation of the clutch & 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, hold up a better & longer, regarding lubrication. Spline
wear, if not lubricated, can lead to spline failure, a $$$ situation.
I suggest a look-see & cleaning & lubrication of the transmission input splines at
15,000 miles since last cleaning & lubrication, & then adjust the mileage for the
next following time, depending on condition. End play on the input shaft can
cause a quite-grabby clutch operation; that can happen cold and/or hot. More
often when hot. To fix THAT, one must remove & open the transmission & 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, &
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 seemed to be more so for the 1979
models. Grabby clutches can also come from a somewhat rare problem, the
crankshaft has excessive end play.
HAS INFORMATION TO FIX THAT PROBLEM.
It is possible for a bad throwout bearing to cause a grabby clutch.
Recommended greases for the splines:
Because of my & others' testing of spline lubricants, over many years, & still
going-on, I have removed all grease & greasing methods from this article you
are reading, & placed them HERE:
You will find the information at item #6 in that article. Please read it
carefully & fully.
EZ-Clutch (and variations): The pre-1981 clutches have a heavier pull at the
handlebars, some dislike that, or cannot easily physically cope with it. There
are several types of modifications to fix this, besides the HUGE expense of
installing a 1981+ clutch with its necessary transmission work. 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.
Bench Mark Works also has it available from their 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 ideas:
There is a round factory tool to centralize the friction disc when assembling
the clutch to the flywheel/carrier. However, your eyeball is good enough if careful.
If you want to make this tool:
The tool, overall, is roughly 133 mm long; the length is NOT in the slightest
critical. In fact, hardly anything is critical. I do suggest making the 20.7 mm
diameter, as shown in the sketch, reasonably close to that. My measurements
are from the factory tool I have:
Here is a photo of all the factory-type tools for the clutch:
The tools are especially useful for the /5 clutch, but you do NOT NEED THE
TOOLS. You can fashion something to hold any of the clutches from rotating
while R/R bolts. You can use long cheap hardware store bolts & nuts to
release the /5 clutch...etc.
Here is a hyperlink to my tools article: http://bmwmotorcycletech.info/tools.htm
In that article will be found information on clutch removal and assembly tools.
Assembling the clutch:
1981 & later models have a lipped seal at the rear cover, not easily replaced....the
transmission must come apart. This lipped seal at the rear is for the clutch-
operating pushrod. Install THIS year & later pushrods, oiled, FROM THE REAR,
rotating it a bit, to avoid damaging the seal (which you will, if you install from
the front, like is done on earlier transmissions)
Here is a major hint. Some of this is NOT factory information:
When you disassemble a clutch, for whatever reason, one of the things almost
always done is to check the friction disc for thickness. This means from one
side to the other. I do it near the outer edge, and at about 3/4 of the way towards
the center of the lining. Other checks are the spring (relaxed mode) height, &
condition of the other parts in the clutch assembly. New friction discs are about
6 mm thickness with some variation, fractions of a mm, over the years. BMW
says to replace the disc at 4.50 mm. On an Airhead, getting to the clutch is easy,
so whether or not to replace a disc at 5 mm or even a bit less, is a judgment call.
You might consider letting it go, so long as the clutch is not slipping in top gear
with heavy throttle & goodly rpm, all of which are worst case for slippage to occur.
One of the big decisions, & this is the HINT, is what parts need replacing, if any,
if the friction disc is going to be replaced. You may hear advice that parts that
push against the disc, on both sides, need replacing. But, how do you know?
There are no specifications on the DISHING type of wear that IS one of the main
reasons to replace those parts (& deep scoring, etc.). Some of us know what
works, & what does not, & we might check 'dishing' with feeler gauges on a
precision flat surface. Here comes your hint...
Measure the disc friction area near the outer edge, then in somewhat, & then
near the inner edge. Do this with a micrometer, not the wide jaws of a vernier
caliper. If the thickness is pretty good for all three checks, you are VERY
LIKELY NOT going to need the other clutch parts. How much difference?
Maybe 0.015" is about the maximum but have seen more that was OK. If less
than that as a variable, you probably can just replace the friction disc.
If the clutch parts are NOT "OK" flat, you can contact such as Southland Clutch to
machine your plate & make you a thicker disc to compensate for that machining; or,
purchase new parts. Many folks just replace the disc, & have to do a clutch job all
over again, soon enough, due to not checking the wear on the other parts.
Southland Clutch; 101 E. 18th St., National City, CA, 91950, (619) 477-2105, can
resurface all models of Airhead worn clutch parts & supply the thicker clutch disc
that is needed after those operations. Dan Levine. Dan@southlandclutch.com
Here is that previously mentioned hyperlink to my tools article:
In that article will be found information on clutch removal & assembly tools
During your assembly (don't forget previous information on marking the parts &
120° assembly), I suggest you coat the edge of the diaphragm spring where it
touches the flywheel & the fingertips areas too, all with thick moly grease/paste....
not very much! This will help the spring fit properly & operate smoothly.
Remember: not too much.
Align the friction disc by eyeball or tool. Torque evenly the clutch bolts. For Pre-
1981 models you need some sort of long bolts & some spacers from a hardware
store unless you have the BMW or equivalent tools. I mentioned those long bolts
earlier,...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 3 or 4 of these long bolts...three will
do, as the clutch has 6 normal bolts, three can be spread at 120°...you will also need
spacers for them. Install these long bolts evenly, criss-crossing while tightening
them evenly, bit by bit, until the clutch is pulled together, only moderately. THEN
install the original bolts; torque them properly one by one. For the 1981+ clutch,
replace the clutch bolts AND the special vibration-proof washers.
Flywheels, clutches, and their bolts:
SOME 1980, & all 1981 & later Airheads used Clutch Carriers, no longer are they
Did you have the flywheel off? Engine rotated some? Need to find out which
crankshaft bolt holes & flywheel holes should be lined up? Five choices!
Here is an edited question & reply I did to the Airheads List:
"" I removed the fly wheel at top dead center (OT mark) but when I installed the
seal with the installation tool I ended up rotating the crank. How can I ensure
that I am at top dead center so I can reinstall the fly wheel correctly?""
Since you have the flywheel off, I certainly hope you have a crankshaft stop of
some sort, at the alternator bolt. If you did not, you are in danger of doing major
damage as you install the flywheel....so, do it...and hopefully the crank has not
already moved forward. If you think it moved forward, see my article & the sketch
from Tom Cutter....both are on my website. It is Article 60, sub-section 2
direct link: http://bmwmotorcycletech.info/flywheelremovalwarning.htm
I am not much in favor of removing that crank stop (so as to turn the engine with
the rotor bolt), to find TDC, because if you should then allow the crankshaft to
move forward, you could be in a world of trouble.
The safest way for you to go would probably be this procedure:
1. Remove the valve cover on the left cylinder & remove left & right cylinder spark
plugs so the engine is easy to rotate.
2. Place the flywheel into any bolt-hole positioning, lightly putting in a few bolts.
3. Rotate the flywheel slowly in the NORMAL direction, which is ANTI-CLOCKWISE
as you face the flywheel from the rear. Watch as the left EXHAUST valve CLOSES.
Rotate more & watch the left INTAKE valve. After the INTAKE valve closes,
continue to rotate in small amounts, shining a flashlight into the spark plug hole.
You will see the piston come fully out, then reverse. The pushrods, piston at near
or fully outwards, should be easy to rotate by your fingertips, & a double check is
that both valves are fully closed.
4. Rotate the flywheel CW & CCW small amounts until the piston is fully outwards,
eyeballing it is good enough! There is an explanation that could include the 72°
per bolt hole which seems like a lot; but, a full explanation would include it being
less because the piston moves rather slower than those degrees might tell you, as
the piston comes out and near OT (the piston rod is extended), but we can disregard
that here. We can also disregard using a dial indicator, etc.
5. Some might use a round tip metal rod for 'feeling' the piston. Do NOT bugger-up the
spark plug hole. Do NOT use a pencil, it could break.
6. With the piston now ~~fully outward, if the OT mark is not someplace IN/near the
timing window, remove the flywheel & reposition it so OT is in the window, or
very close to.
7. You can skip removing the valve cover in step 1, & then skip step 3, if you feel OK
about 'feeling' for the piston coming outwards. It does not matter which stroke you
are on, just that the piston is fully outwards relatively closely. I often do it with
the round-tipped tommy-bar in the standard tool kit, through the spark plug hole.
Turn the engine, if you do it this way, very slowly and gently, so as to not let the
tommy bar hang-up & bend the spark plug threaded-hole metal.
HINT!.....The early R65 and R45 had smaller clutches than the larger engines did.
The 1989 & 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; & 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; 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!
Early /5/6....to 1974
had 10 mm flywheel bolts used on 93 tooth flywheels. There were
two lengths installed. I will NOT reuse them. Torque them to book specifications,
dry. The flywheel was 11-22-1-256-966.
/6 in 1975 and 1976 had 11 mm flywheel bolts on a 93 tooth flywheel. The flywheel
was 11-22-1-262-070. 11 mm bolts were used on all later models.
/7 for 1977 through early 1978, NON-emissions timing bikes had 11 mm flywheel bolts
on 111 tooth flywheels. The flywheel was 11-22-1-263-788.
1978-1980 WITH emissions timing bikes had 11 mm flywheel bolts on 111 tooth
flywheels. The flywheel was 11-22-1-336-380.
Flywheel mounting uses the mentioned larger 11 mm bolts on all models after the
1975 change from 10 mm bolts. Threads were ORIGINALLY to be clean, dry, NO
BMW Service Information bulletin (we call them SI's), November 1991, #11-049-91, sub
number 2495, & 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), this is with cleaned threads, BUT... the
threads were to be OILED! BMW specifically said that the bolt limits would NOT reach
their limit of elasticity at that torque, & 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, &
applies to 1981+ models....certainly not the smaller /5 & very early /6 10 mm bolts; which
need replacement upon each use, which the 11 mm do not unless damaged. Those
early 10 mm bolts on the /5 & early /6 are absolutely not to be torqued to such high
values. There have been a lot of different specifications on flywheel bolts over the
years. As noted, there were two lengths of 10 mm bolts used.
I use, clean & dry (or faintly oiled, by cleaning with kerosene with a BIT of oil in it),
torques of 42-45 foot-pounds on the 1973 & earlier engines. For the 1974 I use
52-55 ftlbs. For 1975 & later up to the 1981 models, I use about 75 to 80 ftlbs. I use
about 80 ftlbs, clean & dry threads, on 1981+, but am OK with slightly oily, if you wish.
and, clutch cable problems
32-73-2-324-956 cable is 1460 mm or 1495 mm long; 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; the sheath portion is 1155 mm long
32-73-2-324-959 cable was used on R65 Euro, 86+RS. 1386 mm long
32-73-1-230-041 cable is 1320 mm long; the sheath portion is 1085 mm long
32-73-1-230-042 cable is 1460 mm long; the sheath portion is 1225 mm long
3273959 is 1361 mm long, sheath is 1130 mm. Needs confirmation. Believe
was on R45/R65
3273694 is 1469 mm long with 1242 mm sheath, needs confirmation, believe
was used on R45/R65 with high bars.
32-73-2-324-956 cable is 1520 mm long, the sheath is 1285, used on GSPD, some others.
32-73-2-324-960 is 1625 mm and is on K1100LT
3273957 is 1410 long, sheath 1180, used on R80, R100, Mystic
I have a LOT MORE information on various clutch cables, used with various bars, etc.
The above may not be 100% accurate now.
See www.siebenrock.com for more control cable information
Below is a snippet copy from my control cables article covering WHY
cable problems arise. Below this box are more details.
|1. Throttle cables on the Airheads: LEFT cable failing at the carburetor,
due to the throttle cable being bent as owners checked the oil via the
2. The bushing at the clutch lever casting assembly at the handlebars that
the clutch lever rides on would wear (on BMW's it is a nylon sort of
material). The result was the lever being able to move up and down,
allowing angular motion. If loose enough, the stranded core of the cable
would start rubbing, or even catching, on the guiding slot in the lever,
and that slot typically had fairly sharp edges. Eventually a strand would
break, failure came soon as more strands broke. The bushings are
easy to replace and not expensive.
3. Poorly made cables, nearly always were AFTERMARKET. BMW cables
are LINED & last a long time, & are SMOOTH with little friction. NOTE
that some poorly made BMW cables HAVE been seen. The areas of
poor cable manufacture are generally at the barrel tip area; some hand
work will fix it.
4. Failure to route the cable properly....typically resulting in too-tight bends
or insufficient flexibility.
5. Lubricating BMW cables....lubrication attracts abrasive dirt and may (?)
swell the liner (a nylon-like material).
6. Using too many cable ties to frame, etc....so the cable was too rigidly
7. On ALL bikes: failure to ensure that the cable end barrel's can rotate
smoothly (hand file the barrel, sometimes the crimped part at the end
needs attention too, depending on style). Lubricate barrels with moly
grease or moly-oil. This also applies after gunk/wash jobs: re-lube those
barrels! In some instances the rounded area of the fork in the clutch
lever at the transmission (where the BARREL FITS), fits too tightly.
***Breaking Clutch cables often?....see above box and below, under
NOTE: BMW clutch cables are lined with a plastic material. DO NOT OIL THEM.
The ONE exception was the earliest /5 bikes, which came from the factory withOUT
the nylon-like internal lining. I suspect only a few low mileage /5 bikes are around
these days with those earliest cables. Aftermarket cables generally do NOT hold
up, as they do not have such a lining.
BMW's cable suppliers have sometimes done a lousy job. Some BMW replacement
cable barrels do not rotate smoothly; you should file them so they do. A nastier
problem is the top (at bars) crimped portion that do not fit the lever slot properly;
there can be interference; the cable will foul on the lever. BE SURE TO FIX THAT;
use a fine not coarse file. Another problem (reported to me) has been MISMARKED
FIRST be sure the clutch cable is routed properly, & tied down only once at the
frame. That tie, which must be only barely 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 angular
UP & DOWN play; if it does, the nylon bushing IN THE BARS LEVER AREA needs
replacing; make sure the waverly washer IS in the lever depression area for it.
BE SURE that with lever movement in any direction (in-out, up-down) 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
The adjustment is not supposed to be exactly the same on all models.
practice, while the new method will work OK for all Airhead Clutches, I prefer to
use the old adjustment method for the early clutch. The 1981+ clutch adjustment
MUST be made with the new method. My recommendations are below:
1. For pre-1981 clutches (some few 1980 had the later clutch with carrier):
The adjustment at the lever at the back of the transmission sets the free-play
clearance at the BARS lever; the adjustment of the outer cable sheath at the
BARS lever sets the adjustment at the lever at the back of the transmission.
You want to end up with about 3 mm free play at the bars lever JUNCTION,
that is, the outer angle of the lever to casting assembly. Shown in your owners
booklet. When the bars lever is ~ half-way through its actual pressure range,
the clutch lever at the rear of the transmission should be PARALLEL with the
transmission rear case. When you are done you should ALSO have
APPROXIMATELY 2 mm of free play at the lever at the transmission rear cover.
2. For the 1981+ clutches the adjustments are done a bit differently. The difference
is that the distance measured from the forward surface end of the barrel in the
fork of the transmission-located lever, to transmission case where the cable
comes rearward-through, should be 201 mm. There are also factory books that
say 201 to 203 mm. BMW was never really clear on what part of that barrel the
measurement was to be from...rear edge? middle? forward edge? As I noted, use
the forward part of the barrel. The TOP cable adjustment...yes, at the BARS,
sets that 201 mm distance.
The next adjustment is the bolt & its locking nut in the lever at the transmission.
Adjust for 3 mm of free play at the bars lever. If you do not know how to do this:
Loosen the adjustment at the transmission lever a fair amount. You can now
move the handlebars lever easily, & if moved far enough, you meet goodly
resistance from the clutch. The amount of 'easy' movement, with NO clutch
action, is to be such that the lever opening is 3 mm.
When the bars lever is not being touched, the transmission lever will be ~4°
leaning AFT of the transmission rear cover. Make a simple tool from a piece
of coathanger or whatever, marked for 201 mm, to check the 201 mm. Don't
worry about the 4°, just know that with #1 eyeball on the transmission lever,
it IS to be slightly rear leaning. Do these adjustments with the engine COOL.
The reason the clutch levers are set this way is to ensure that the transmission lever
operates in the most efficient leverage position. If you do NOT adjust it this way, &
have the lever too rearward on the 1981+ transmissions, the rubber boot at the
transmission clutch rod area will, or can, LEAK OIL. Be sure that you set the 201 mm
distance and the bars lever distance correctly!
Now & then someone will complain that their bike, after sitting, more often in
high humidity areas, has a clutch that has failed or is stuck. You can pull the
lever back, it perhaps feels normal, but the clutch will not release & if you put
the engine crashingly into gear, the engine stalls.
The problem is that the clutch disc has frozen to the adjacent parts. You can
fix it by replacing all the clutch parts with the latest items, which are not cheap...
OR, you can try to force the clutch to disengage. There are several methods,
including pushing the bike & shifting into second gear....etc. You can pry at
the clutch through the timing hole...I suggest you DO NOT!
I prefer to try the following things first (it can take two or three tries!):
(1) Put the bike on the center-stand; SECURELY jack the bike at the rear frame
crossover (swing arm area?), ....have the rear wheel a bit off the surface.
HOLD the front brake! Start the engine in first gear. Do not touch the clutch
lever. At some moderate rpm, suddenly give very hard pressure with your
right foot on the rear brake. That may force the clutch to release. Try twice.
If no help, go to step (2).
(2) Warm up the engine, so it starts easily. Push the bike to the street. Start
the bike in FIRST GEAR (depending on model, you may have to pull in the
clutch lever at the bars to allow the starter motor to crank the engine to
restart the bike). Ride the bike down the street at 5000 or more rpm in first
gear. At a convenient & safe time, suddenly pull in the clutch lever at the
bars & hit the front and rear brakes VERY HARD. Try this up to three times
if it does not let the clutch release immediately. If no luck at all, you will
have to remove the transmission, & work on the clutch...or, try prying at
the clutch through the timing hole.
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.
06/08/2012: Completely re-do the clutch levers adjustment area for clarity; clean up excessive use of
fonts, colors, emphasis.
06/25/2012: Expand upon stuck clutch information
06/28/2012: Clarify cable problems and clutch adjustment.
09/04/2012: Add section on setting flywheel and crankshaft to correct alignment. Add QR code; change
Google ads arrangement; add language button.
12/12/2012: Remove end play adjustment details, as is now in the flywheel removal article, 60-2
12/24/2012: Add paragraph on clutch wear dimensions.
04/28/2013: Clarify a few details, remove some redundancies, clean up article, add hyperlink to the
disc alignment tool pdf.
05/16/2013: Expand the section on throwout bearing parts, adding emphasis and an update due to a
bad late style in a R100R that was reported.
08/15/2014: Correct item 3 from CW to CCW; correct flywheel number from -906 to -966
03/17/2015: make sure hyperlinks work properly
07/22/2015: add more information regarding lower end of clutch cable (barrel) and the associated clutch arm
and add specific section on greasing splines, removing prior information.
12/09/2015: Go through entire article. Increase font size, change separation lines, fix meta codes, duplications, etc.
02/04/2016: Begin minor updating, and completion of 12/09/2015 items not then fully finished.
© Copyright, 2014, R. Fleischer
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