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Throttle & clutch cables. Clutch lever (at bars) bushing.
Confusing changes? >> throttle cams & gears. 
Speedometer cable rubber boot at transmission.
Speedometer & tachometer cables.
Control assembly perches/wedges.

Eliminating confusion: replacing throttle gears/cams assembly. 

Copyright, 2014, R. Fleischer
7B & K30

INTRODUCTION...and description (and some fixes) of problem areas:

In my shop I saw many control cable failures from these things:

1. Throttle cables on the Airheads: LEFT cable failing at the carburetor, due to the throttle cable being bent as owners checked the oil dipstick. Do NOT bend the throttle cable at the left carburetor when checking your oil.  There is no need for the oil dipstick to be overly-tightened.  Bending the left throttle cable is a prime cause for that left cable to have increased friction, possibly spread some coils on the wrapped sheath (making that carburetor fun & games to synchronize, if bad enough), & eventually you might break an inner strand...usually where you can see it between the throttle lever on the carburetor, & the sheath.  A single strand found broken (You DO inspect these cables regularly, don't you?), will usually cause other strands to eventually break from the same reason why the first strand broke....this will...or can...result in total cable failure in a few hundred miles or so.

2. The bushing at the clutch lever at the handlebars is a replaceable nylon sort of material. If worn the result is the lever could move up and down & allowed angular motion.  If worn enough, the stranded core of the cable would start rubbing, or even catching, on the sharp edged guiding slot in the lever. Eventually a strand would break, failure came soon as more strands broke. The bushings are easy to replace and not expensive.  If your new bushing does not finger press into place, heat the lever first.  The Nylon-like bushing is 32-72-1-232-662 and has been used from 1976 onwards.  That nylong bushing may need light reaming for a good fit to the pin.  If you do not have a 8 mm tapered ream, you can use VERY carefully selected drill bits, to progressively remove a TINY amount of material, a few thousandths at a time....until the pin fits easy, but not loose, push-sliding fit.   The lever has a recess, and in that recess must be a waverly washer, 32-72-1-230-871.    I recommend the sharp edge of the slot in the clutch lever be filed smooth.  
Be sure the crimped end of the cable that fits into the clutch lever at the handlebars is also not fouling the lever.  Be sure the barrel can move smoothly at the clutch lever (tip) located at the rear of the transmission. MANY transmission-mounted clutch levers require a bit of filing and sandpapering to allow the barrel to rotate smoothly; the problem is that the curve for the cable barrel is very slightly too small...easy to fix.

3. Poorly made cables, usually AFTERMARKET.  BMW cables are LINED and last a long time, and are SMOOTH operating with little friction. NOTE that some poorly made BMW cables HAVE been seen.  The areas of poor cable manufacture are generally at the barrel & barrel tip area; some hand work will fix it.

4. Failure to route a cable properly....typically resulting in too-tight bends or insufficient flexibility. 
Do not tie the throttle cables down with wire-ties/wire-wraps where they were not supposed to be tied down; generally there is ONE ONLY.   The clutch cable has only ONE tie-down, on the right frame tube.  Do not miss-route cables, they must NOT have sharp bends. 

5. Lubricating BMW cables....lubrication attracts abrasive dirt and may swell the liner (a nylon-like material). Only the very earliest original-as-shipped /5 cables were not lined.

6. 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!

I recommend lubricating the barrel ends at the carburetors after EVERY bike washing!...I like to let them dry overnight first.  Failure to do this can lead to broken cables. 

A listing of control cables by part number, lengths, etc., is much further down in this article.

Why the complicated throttle assembly design?  Cleaning and lubrication.

Occasionally I read or hear commentary about the complexity of the BMW throttle assembly.  It requires cleaning & re-lubrication every few years, has synchronization marks on its cam gear & throttle sleeve.  It is slightly tricky to assemble.  Sometimes, if not mostly, the commentary is negative.  This reflects on the commentator, who does not understand the design, which is SUPERIOR to most motorcycle throttle control assemblies.  The BMW design is quite good; this includes whether it is the single-cable type (I prefer that one as the carburetor synchronization is better & longer-lasting), or the dual-cable type. 

The throttle cam gear assembly was designed by BMW to be NON-linear.  As the throttle is initially rotated from off to on, the cam design is such that the throttle cable initially moves a rather small amount for throttle rotation amount.  As the throttle is rotated more & more, the cam moves the cable inner strands more, in proportion, for any particular amount of throttle movement.    The advantage is that as one takes off gently from a stop, there is smoother control over the carburetors; there is none of the jerky sensitivity of the throttle that one finds on many motorcycles, particularly some that area fuel injected.

BMW used different throttle cams for the various types of carburetors (primary difference is with 32 mm vs. 40 mm carbs)  AND for different sized engines.

FURTHER, the design is such that the throttle cable is a straight-pull; there is NO bending of the inner cable as in many other types of designs; thus the throttle cable at the bars-end can be expected to last a very long time, without fraying or breakage.  BMW even specified a Nylon-like lining material in the cables.   Cable breakage at the throttle at the handlebars is almost totally unknown.  It is the other end, at the carburetor, that will fray & break...typically because the rider does not keep that end barrel lubricated; and/or, bends the throttle cable while checking the oil level dipstick.

The human hand is fastened to the human wrist & there is only so many degrees of easy movement in the average wrist, before you'd have to release the throttle, and re-grip it further along.  Therefore, there are restraints on the amount of throttle rotation per amount of cable movement. This is set by the throttle cam shape, & by the gear ratio between the cam & the throttle tube.  BMW made a good compromise between this over-all 'throttle gear ratio', & the need for relatively good response for small throttle openings yet also attaining maximum throttle.

If you lubricate the throttle gears/chain assembly now & then, and the cable barrel ends, wear will be slow.  Wear is almost entirely the teeth on the cam and teeth on the throttle.  The teeth are usable until they get worn to the grumbly-feel point, or, overly pointed; some longish time after which they strip. 

Throttle gears & cams, some specifics/problems:
There are... or can be... complications involved if you replace the throttle assembly gear-cam and/or assembly cover.  They are not the same between early & late models, are not the same for 32 & 40 mm carburetor models....and some parts are no longer available, & you need to know which later parts are correct ones that will fit your bike...and it is problematical with some dealership parts departments if you will get the right ones, so bring along the old parts.   Know the details, see below, because JUST having the old parts along is NOT NECESSARILY going to tell you...nor the parts department... everything you need to know, depending on your bike's throttle parts.  There are even complications from installing different master cylinder piston sizes, for those MC that are mounted on the handlebars as part of the throttle assembly.  A knowledgeable parts department person can be very helpful; often, this means a NON-dealership company.

The throttle assembly parts have caused confusion mostly because BMW changed the design of some of the cams & the cam cover (especially for SINGLE throttle cable versions) in the twist-grip throttle assembly.   Some earlier parts like the original cam gears are NO LONGER AVAILABLE (so combinations of later ones must be used).   

BMW's infinite wisdom (??), does NOT list the throttle assembly in the carburetion section of literature; rather, it is in Section 32, which is STEERING!  

BMW also modified the top cover and gasket of the on-bars rectangular brake master cylinder, mostly due to warpage and leaks. See:  

The proper
cover plate to use with the later cam assembly is:   32-72-1-457-050.    
The cover plate, 32-72-1-242-561, UNDERSIDE, was flatter at the screw hole. 
The newer plate has a round protrusion at the center, and that is about 1/2" diameter & maybe 1/4" deep. 
The throttle cover was 32-72-1-233-538 for the earliest models.
The new cams are thinner, don't fit the old assembly cover.
The cam assembly for the 40 mm carburetors is now 32-72-1-457-081.
The cam assembly for the 32 mm carburetors is now 32-72-1-457-080.
The throttle TUBE did NOT change.
The cam gear for the R65 series is 32-72-1-238-378.

Be SURE what you purchase will fit!!   The throttle assembly has been a PIA, and it may be best for you to contact knowledgeable Airhead parts folks, such as at Ted Porter's Beemershop, if you don't understand.

Anton Largiader did an excellent article on these above items:

Anton also did a great article on control cables:

You may find differences in part numbers between Anton's article & mine, regarding cables; chart is way down this article you are reading.


Some folks have problems with unfastening ...and especially with re-assembly ... of the throttle cam/tube/chain/cable.   You do NOT have to loosen anything at the carburetors nor the T connector under the tank (one cable models have those).

First, unscrew the single large slotted screw in the assembly cover.  Lift off the cover plate.  Notice that the throttle end of the cover plate has a curved and downwards section that sticks into a corresponding slot in the throttle tube.  That keeps the throttle tube captive once the cover is in place. 

Notice that the throttle tube has gear teeth at its inboard end and notice the mark stamped into or next-to a tooth, and there is a corresponding stamped mark on the CAM.  When re-assembling, the marks must be lined-up to point to each other.  

After you re-grease the cam, etc., and are ready to re-assemble, line up the two marks, throttle meshed to the cam teeth.  Hold onto the throttle, pull on the CABLE(s) SHEATH(s);  hook the sheath(s) end(s) to the place provided for it (them), in such a way that it(they) is/are bottoming in the machined area.   You will be pulling against a moderate spring tension.  Do not let the cam slip, versus the throttle tube, you want the identifying mesh point marks to continue to line-up.  With your left hand holding the cover, and right hand on the throttle, carefully push the cover into position.   The cover will fit perfectly, no special force needed.  Install the large head slotted screw.

Some throttle assemblies have a friction screw, a large knurled shiny 'thumb-screw" operated by your finger tips, you can use it if you wish to help you. 

If you have the type of throttle on the bars with ONE cable coming out of it, you have (unless you are riding a BMW single!) a tubular junction, a T connector, under the tank.  That has an adjustment for the single upper cable free play. Proper adjustment is to take out most, but not all, of the free play (rotate bars from left stop to right stop to be sure you have free play). I like a bit under 1/8" of free play at the throttle sheath at the bars.  Be sure the rubber sleeve on the nose of the T connector is in good waterproof condition.   Failure to have the cable properly adjusted at the T connector can result in insufficient throttle movement relative to the carburetors; you will not be able to get full throttle; or, if too tight, idle will never be stable.  These bikes have a similar T connector for the CHOKE cable.   Neither T connector innards are normally to be lubricated.  If yours is not perfectly smooth operating, you can disassemble them and clean the insides and then coat the piston with a dry lubricant like MolyKote M-88 or even graphite powder as used in locks.  A dryslide spray, as used on bicycle chains, can also be used....spray the tubing and piston, allow to dry a few moments, then assemble and adjust the free play.

In your on-bike tools & parts, you should have a spare clutch cable, & a spare throttle cable(s).     There are all sorts of lengths of cables, be sure you have the correct ones for your model, your carburetors, & your type of bars.  BMW often prints the actual ordering cable number on the cables in white print.

Speedometer and Tachometer cables:
If you have a jumping needle on either instrument, first clean & lube the instrument, especially the gears & shaft bushing on the speedometer.  If that does not fix the problem (some odometer sections can have the gear mesh adjusted very simply...lightly grease them too) then either replace the cable or force lubricate the cable with a decent lubricant.  A graphite type works OK.  There are cable lubrication devices, but most of you will likely just remove the cable, and let a decent liquid lubricant drip down the inner cable, drops at a time. These are last resort 'temporary fixes'; otherwise it is overhaul the instrument time.  One can test the instruments using an electric drill and making an adaptor from an old end piece of cable, or squaring a nail. The drill motor preferably has a direction reversing switch.

Speedometer cable rubber boot at the transmission:
The speedometer cable rubber boot at the transmission must be replaced if it is in poor condition. Failure to do so will result in water entering the transmission causing a VERY HIGH repair bill.  The top of this boot MUST fit tightly all-around the speedometer cable.

REMOVE the 10 mm hex hollow bolt that holds the negative battery cable lug.  The bolt is also the breather for the driveshaft (& the transmission on most Airheads).  The hollow bolt SHOULD HAVE TWO flat washers, one under the lug, one outside the lug, & there should be a waverly type locking washer against the head of the bolt.  You can modify the battery cable lug by snipping it JUST enough to let it push over the hollow bolt.  This allows you to disconnect the battery without completely unscrewing the hollow bolt.  YOU MUST have the WASHERS, so that you will NOT spread the cut lug during during tightening.  NEVER over-tighten the hollow bolt!  

Installing the new boot:

Method #1:  Push the rubber back on itself & push up onto the cable with the large end upwards (pushed back on itself).  You will then be pulling the large end downward, so the small end stays upwards.

Method #2:  Install a piece of shrink tubing; lubricate it with one drop of dish detergent. Push the boot up.  You can do this without the tubing too.

Method #3:  It is possible to use a tapered device such as the tip off caulking tubes, & with removal of the end parts, use the taper tool, with perhaps a bit of grease, to slide the boot up, etc.  

It is critical that the rubber boot does NOT allow water to leak into the transmission.  This has been the cause for a lot of $$$ transmission repairs.  The typical indication of water in the transmission is oil that looks like creamed coffee.  My suggestion is that you seal the new boot.  Some use a lot of grease inside the boot.  I do not like that idea, it WILL defeat the breather design.   If you look at the outside of the cable drive part that is located inside the cable-fitting-hole-area, you will see that it is grooved for a reason, vapors must be allowed to escape, plus the oil must be free to return & stay in the transmission.   Some folks use a zip tie over the top small end of the boot. That's ALSO a poor idea.
This is especially so if the zip tie is a larger one or is just a bit too tight.  The tightening of the zip tie makes the top of the boot squeeze OUT OF ROUND, & can actually make things WORSE for water getting inside.

Sealing the boot properly is simple.  AFTER you install the boot, including pushing it completely over the flange of the adapter in the transmission hole, then push the top of the boot (the top is the small upwards end of the boot) downwards some, so as to expose more of the cable sheath that was inside the top of the boot. CLEAN that exposed sheath area with acetone or other fast drying solvent that leaves no residue, using a rag.  BE SURE it is well cleaned.  Put a small amount of black RTV sealant or your sealant of choice, at the top, smooth it nicely with your finger; then slide the top back up to normal position, then reseal with your fingertip again.  Smooth the sealant junction with your finger-tip so it looks nice, & let dry overnight.  After the sealant cures overnight use something like Armor-all or 303, etc., on the entire boot.  That greatly prolongs boot life, as the rubber compound BMW uses is adversely affected by smog & sunlight.  Coat it again now and then.

Accordion boot at driveshaft, breather....& swelling:
The hollow bolt is the ONLY breather for the transmission (on most models) and the driveshaft.  Clogging is often only noticed in very hot weather, when the large accordion boot would swell up.  The pressure can force oil out of the boot.  The earliest 4 speed transmissions did not have the vent at the rear of transmission, above the output seal (forward of the U-joint flange area).  Thus the accordion boot tended to swell-up, as the driveshaft area heated up.  Leave it alone, unless you love playing with things like removing the transmission, removing the flange (special tool), drilling or otherwise machining a tiny hole in the transmission output flange area (at 12:00).

Control cables, additional notes:
Some of this article's below sizing information may, or seem-to, conflict with Anton Largiader's page.  We took the measurements somewhat differently (and there could always be errors). UNfortunately, some of my information was lost, when/if I find it, I will add it to this chart. 

There is additional information here:
That is their English start page, but navigation keeps changing, so you will have to navigate the website to find the cables, & you might have to do a site search, & then translate to English, perhaps wholesale translation, via Google (Google browser users can turn on automatic translation service; or, use their translation page).

It is easy to find a part number for any particular bike model & year, on any on-line fiche.  What is NOT easy is to find out, at least not always, if yours are high, medium, or low bars; but, especially, if you are making changes, not just in the bars, you cannot search for cables by length. In my article you are reading, in the chart below & in Anton's article, you CAN see the lengths!  Note that SOME cables come with the rubber boots at the end(s).

R65LS low bars are black version of the R90S/R100S bars.  R65LS high bars are similar to /6 and /7 US shipped Hi bars models, but are black.  
Fuel, or throttle cables, may be listed as Accelerator Bowden Cables.  In fact, any control cable is often listed as a Bowden.

Refer to for further information on cable lengths and what is meant by "length" and "free length".
NOTE that my information is primarily for bikes shipped to the USA.   In some instances the Euro bikes, or Canadian bikes, etc.,  have 40 mm carburetors instead of 32 mm carburetors, and this MAY require different throttle cables.  In my chart below I may have the part numbers and length for some of those, and if so, they are identified for you.  If replacing cables due to wear, there is a BMW part number printed on them!

Model of BMW, if known

Where used

Length, sheath & over-all.
FL = free length.

BMW part number


/6/ 1984 or 1985


1386, sheath 1155, overall 1410

overall 1386



LOW bars for both of these.

/5 standard


1320, sheath 1085, overall 1345


low bars, standard

/5 Hi bars


1460, sheath 1225, overall 1485


Hi bars

/7 on, RT, GS, G/S


1495, sheath 1285, overall 1520


Hi bars






R45 and R65


1361, sheath 1130, overall 1386


Lo bars

K100, K75, K1100




Hi bars

R45 and R65


1469, 1242, overall 1495


High RT & similar hi bars

R80/100 Mystic, R100R
and many early Airheads with Hi bars


1410, 1180, overall 1436



Many Classic K models


1510 overall


Lo-medium bars


528 mm, some lit says 517 mm


40 mm carbs


1158 mm


32 mm carbs


1118 mm


32 mm carbs


32 mm






LEFT cable
RIGHT cable
    When a GS is upgraded to 40 mm carbs, probably will use above two cables.    

91-95 R100PD
R100R; R80R R100GS, PD





84 FL




40 mm carbs, LEFT cable.

40 mm carbs, RIGHT cable.








Hi bars, upper cable

All, since ~1976


Clutch lever at bars





waverly washer

Nylon-like bushing


Perches, Controls wedges:
The part numbers for these wedges are: 32-72-2-072-233; 32-72-1-232-929; and 32-72-1-242-626, etc.
For photos of them in use, see:

They have used various names, including Perch (some use that word for handlebar risers, however) and commonly WEDGE.  The German word is Keil.

These tiny metal wedges keep the controls from slipping:
They are shown on BMW fiche on the sketches of the handlebar controls.  See article 76.
These came in different finishes, depending on year, etc.

04/26/2007:  add information on throttle gears and cams
01/14/2010:  Remove clutch cable from title, minor changes in article to clear up grammar & ensure clarity.
06/16/2011:  Clean up some, clarify a few details
09/24/2012:  Minor editing; add QR code; add language button; change google code
11/13/2012:  Add more to cables sections, show article in two places, 7B and previously unused 64.
01/06/2013:  Add Perches section
04/06/2013:  Remove as duplicate article 64.
05/09/2013:  Incorporate speedo rubber boot information, prev. in miscl.htm.  Add another link to another of Anton's articles.
05/24/2013:  Add introduction
05/15/2014:  Recheck article, very minor changes, mostly for clarity; add hint on assembly of throttle and cam
08/03/2014:  Somehow my own cable chart listings disappeared during the 7B and 64 interchange.  Added a blank table, and will attempt to re-constitute what I can find in my existing notebooks.
08/05/2014:  Started filling in that table.  Next to do:  SNABB and Fiche work to be sure table information is correct, and expand usage, and clarify partial part numbers.
08/08/2014:  Finished for now.   Cleaned up and uploaded 10/04/2014
07/22/2015:  add more to section about clutch cables (regarding the transmission located lever)
02/05/2016:  Increase font size.  Narrow the article.  Metacodes updating, ETC.
05/25/2016:  Revise article, eliminate redundancies.  Add part numbers for waverly washer and lever bushing. Minor clarifications. 
12/06/2016:  Expand information on perches/wedges, for clarification.
12/07/2016:  Add video on how to install boot.

Copyright, 2014, R. Fleischer

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Last check/edit: Sunday, December 25, 2016