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BMW Airhead Motorcycles:

Hardware (metal, rubber, etc.) etc.
Plus brief discussion of 'locking' methods for hardware

Pozi, Reed & Prince, Frearson, & Phillips screws, near the end of this article.

Includes information on some items & references not found in my references page (78A):

Copyright, 2014, R. Fleischer

General notes on parts:

BMW has used two methods over the years of part 'coding'.  This is applicable to fiche, CD's, and other literature.  A list of these codes is in article 69:

Stainless Steel:    Many folks have purchased stainless steel nuts, bolts, etc., which are available individually, but also in bulk form (including large pre-packaged sets for your bike).  DO NOT FAIL TO USE AN ANTISEIZE COMPOUND ON THE THREADS.  Failure to do so will result in eventual GALLING, a form of WELDING.   You may also want to DEcrease the torque value a bit.    Please take note of the fact that, in general, SS parts are NOT as strong as the steel (whether cadmium plated or otherwise treated, or not, by BMW) stock parts.  Be especially cautious where original parts were graded 10.9 or higher.

This article lists, AND IN SOME INSTANCES DESCRIBES, hardware items for BMW Airhead motorcycles & LIKELY HAS ERRORS.   It was not possible to physically look at every part listed here.   Parts numbers & descriptions were taken from a Snabb Katalog & checked against a 1995 printed Parts List.  MOST WERE CHECKED checked against my own stock of parts; a few were checked against on-line fiche.  A small amount of input was from others.  

BMW on-line fiche is not as fully descriptive as some other types of BMW parts literature.  Most of you will use only the on-line fiche.  Here is a good source of such on-line fiche:

Be SURE you understand that what shows in such literature is either the original & still valid part number, or an updated part number (which COULD be the same part); or, in many instances, the part is a LATER part, that BMW says can substitute for the original part.  There may be a transition date listed.  DO NOT take the dating information to always mean the original transition date.

BMW descriptions in its literature are sometimes WRONG!   In ILLUSTRATIONS, BMW may OFTEN show a piece of hardware...or other item...  that is NOT the actual part.  An mild example: an actual Allen bolt is shown in the illustration as a screw or hex head.  Especially be aware that BMW sketches (often the same sketches are found in Clymers and Haynes manuals), can be VERY misleading on order of assembly, and misleading as to whether...or not... such a part is actually used on YOUR MODEL.  This is very particularly true in one critical area, the illustrations showing all the various parts for a particular assembly of the oil filter canister area.  Same for the front forks internals.  DO NOT think that ALL those parts will necessarily be, or should be, in YOUR bike.  Clymers & Haynes have messed this up even further!!

BMW may call some parts by names that, in translating their German to our English, do not mean the same thing; this is especially egregious with the names of bolt & screw styles, particularly head styles.

BMW has sometimes kept the same part number after making changes to the part.  In most instances this is of no major concern; in many instances the updated part is better for some reason or other.   Sometimes there are problems.   Here is another MILD example:  BMW has changed some of its nut & bolt head sizes.  The same part number is being used for a nut that originally needed a 19 mm wrench, & the newer shipped parts are for 18 mm wrench, a size of wrench that is NOT standard for BMW Airhead motorcycles, but is for other BMW bikes.  Unless you want to carry the non-standard wrench in your bike's tool tray, you should be aware of this.  In many instances, the dealer will have BOTH sizes available in the same box, as the PART NUMBER WAS THE SAME.    I do NOT know the full extent of this problem.  I have seen it in 16 mm heads too. 

ONE of the purposes of this article is to enable you to go to a dealer & hopefully! see the various parts, & then decide what you want. 

Bolt LENGTH measurements are from under the head to the end of the threads.  BMW bolts for exterior use used to be, generally, cadmium plated to prevent rust.  This plating may also provide some anti-seize protection & a more consistent tightening.  BMW has discontinued cadmium plating due to Euro environmental regulations.  Many steel bolts & nuts may well now RUST!  Some may now have zinc or other coatings. 

I am NOT saying to willy-nilly coat all nuts, bolts, screws, etc., with antiseize compound.  You must judge where/when; perhaps consult the Airheads LIST and/or this website.  Use of anti-seize compounds generally requires the torque wrench to be set a bit lower.
  In a FEW instances you must NEVER use antiseize.  One is the rear wheel bolts on the Monolever & Paralever models.

BMW uses, generally, bolts rated at 8.8 strength, but at certain places will use stronger; even as strong as 12.9.    Strength rating is always marked on the bolt heads...and on some smaller screws too.


Ever wonder what the number on the end of a metric bolt really means?  You already know it has to do with the strength of the bolt.  What does it REALLY mean?   Here is your answer:

The strength is shown by this format:   X.Y.    Thus, 10.9 or 8.8, etc.
The X number is 1/100th of the tensile strength in newtons per square mm.
The Y number is 10 times the ratio between YIELD and TENSILE strength.

Example (and the math done for you here) for the very common 8.8 rated bolt:
The X is the first 8.   That means the tensile strength of the bolt is 800 newtons/mm˛.  For your information, so YOU don't need to do the math: that means 116,000 psi.
The Y is the second 8.  That means the yield strength of the bolt is 640 newtons/mm˛.  For your information, that means 93,000 psi.

No, not going to tell you how those numbers came about; nor, how I calculated the PSI;...YOU get to research that, if curious enough!

The waverly washers used by BMW may, in some circumstances, provide LESS holding power for the bolt/nut than NO waverly washer.  Very complex to understand, has to do with the surfaces sliding in relationship to each other, which not only loosens them, but tends to UNSCREW them.  .....and; it was a German company that did the testing that proved all this.  There is a discussion of locking methods, at the bottom area of this article, see: 
Discussion of 'locking' methods for hardware

Here is an article about threads and fasteners, that is relatively easy to understand, and explains things in depth, yet simply:

Some BMW bolts have a non-standard HEAD THICKNESS.  An example of this will be seen at the left lower rear shock mount.

The word 'screw' & the word 'bolt' are sometimes used interchangeably.  Typically screw means smaller diameter, but there is no specification for just what constitutes smaller.   Although there is some confusion sometimes between what is a screw & what is a bolt, in almost all instances "screw" is used for those parts that have Phillips or similar look heads; single slot heads; small screws with such as Torx and many other heads, including allen-heads.   It can be confusing, because 'bolts' are generally described as being used with a nut; but quite small screws used with nuts are NOT called bolts.  Konfuzed?  

"Bolt" is just about universally used with hex-head items, & either bolt or screw can be used with some types of parts.  BOLT used to, long ago, be used when the head of the bolt was either a 6 flat hex or a square, although BOLT was sometimes used for such as Carriage Bolts, which have a domed head with a square UNDER the head, said square fits into a corresponding female hole in the material to be clamped.    MY advice is to simply call threaded fasteners that are under ~1/4" in shank diameter, SCREWS; and, larger ones are BOLTS.

Part numbers on a part MAY not be BMW ordering numbers (numbers found on electrics often are BOSCH numbers or Wehrle numbers, but sometimes BMW numbers are found there too).   Numbers may be partial, that is, abbreviated, and this is common for both BMW and other makers, such as Bosch.  NOTE that all these things apply to mechanical parts, not hardly just electrical parts.   Numbers on assemblies... or any part... may NOT be the same as the BMW order number.  The number on a part might be some non-BMW number; or, a BMW part-assembly or casting number.  If you cannot get a reference to the number from one of the on-line parts listings like A & S, MaxBMW, etc., you MIGHT have that situation.  Ask on the Airheads LIST if you cannot figure it out yourself....many of us are quite familiar with various part numbering's.

PLEASE point out errors found in this article to the author, E-mailing to:

In a few instances below, more than one number is shown for a part.  Sometimes those are actually the exact same part, other times the parts ARE different.  Sometimes I have noted the variations.



BL MU   sheet nut        BMW may listed them as BL MU 4, 2-4; also listed as B4, 2-4 BLMU... these are all the same thing.   These are sometimes generically called Tinnerman nuts in the USA.  They are a folded piece of metal, that are used with fairing parts, to provide a place for a screw to go through one side & tighten on the other side. There are many types of these used on aircraft, musician's electronics chassis, etc.  Some expensive types have a hardened metal nut that floats in a cage, that works exceptionally well.   Modest cost ones work fairly well on the BMW fairings....but I do not like the cheapest of the cheap.  I have the part numbers in the miscl. area, well below.

BL SHR  sheet metal screw.   NOTE this:  6KT BL SHR  hex lens head screw

DT RG   gasket ring
KL         Generally used for the type of C (or E) clip used at the seat holding pegs.
LIN BL SHR   fillister head self tapping screw
LIN SHR  fillister head screw (see note ** below)
LIN SK BL SHR  countersunk head fillister self-tappping screw
LIN SK SHR countersunk fillister head screw
MU  nut
PA SHB  disc ring
SHR  screw   (see ** note below)   Schraube
SK BL SHR  countersunk lens head screw 
SK SHR  countersunk head screw  
STI SHR  studbolt
VSL SHR  plug screw
ZYL SHR  fillister head screw...per book, but is allen bolt??  sometimes, and sometimes another type!!  see below.   ZYL-SHR is usually actually found to be an allen headed type.   zylinderschraube      Compare the American use of cheese-head screws.
6KT SHR  hex screw      -KT-SHR is really a hex head, although the SH might lead you to believe it is a allen type.   HB is supposedly a hex head bolt only. 
ZYL STI  dowel pin

4KT MU  square nut
6KT MU  hex nut

BMW may use the word 'fillister', in its translations to English, differently than in common American usage.  In America, a fillister-head screw is NOT an allen head screw; but BMW's usage MAY mean allen-head, that is, a recessed 6 point socket for use with an allen wrench.   BMW may use socket head, correctly, for an Allen Headed screw. There is further confusion with PANHEAD & CHEESEHEAD screws.

I will try to explain a little of this confusion that you may sometimes see.   Zylinderschraube may be shown in literature as  ZYL SHR.  A TRUE fillister head, in German, is a LINsenschraube, which you will see as a LIN identification.   Could be LIN SHR.  There is further confusion in that ZYl SCHR has been used in some literature.  It is all a MESS!  Generally speaking, a taper under the head type screw is called LIN SK SHR by BMW.  Some of the confusion is due to old translations by BMW or whoever did the old SNABB Katalogs and other literature.   Sometimes the confusion is that BMW has used more than one type of head on a fastener at any given place, that is, changed it over time, & the description might have a new part number, & the descriptive words were never changed, & might not have been correct in the first place.  BMW MAY not show the actual type of part in BMW sketches. 

I still have not seen the proper description for an Allen headed screw in BMW literature.  Innensechskantschraube or inbussschraube.

BMW has sometimes substituted various types of heads; you might order one type & get another type.   This has happened in production for various countries too!

yes...all this CAN be very confusing!   If there is a question, you should consider asking on the Airheads List.

In general I have tried to separate out the confusion, in the parts listings below.


When using on-line "fiche" from such as Maxbmwmotorcycles, etc., do NOT use the hyphens between the numbers.  Simply remove
NOT replace hyphens with spaces.

SOME of the part numbers may no longer be listed in fiche.

Hex nuts:
07-11-9-922-053; -054.  M-6.    Some books show a locking nut; other books show this number being replaced by 23-11-2-322-368.

07-11-9-922-081; -856; 07-11-9-921-076; -077; -074.  M-8.    Some books have the 074 and -081 as locking types;  the -081 is replaced now by 07-11-9-922-825, and THAT by -856.

07-11-9-922-110; 11-11-0-001-104, replaced by 11-11-1-263-903.    M-10.    Some books show -110 as locking, the -110 is replaced by 07-11-9-915-558.
07-11-9-922-122.  M-10 x 1.0 mm.
33-17-1-237-789.  M-10, 12 point.
07-11-9-922-148; -940.  M-12 x 1.5    NOTE:  may be 18 or 19 wrench size.
07-11-9-921-631; -633; 07-11-9-901-309.   M-14 x 1.5

Security nuts:
similar to Nylocks; that is, they have plastic inserts.  BMW also has used other types of security nuts, some are here. Sometimes BMW will identify a nut as a security type....maybe it is, maybe it is not! Do NOT depend on the numbers here to be security nuts, without LOOKING at one.
07-12-9-922-404; -452.   M-4.
07-12-9-922-411; -410; 07-11-9-922-035;  12-31-2-322-422; 07-11-9-921-038.   M-5.
07-12-9-922-416; -417; -058; -800; -807 ; -704.   M-6.
07-11(and 12)-9-922-053.  M-6.  Some books show this as a locking nut; other books show this number being replaced by 23-11-2-322-368.
 07-12-9-922-428; -427; -713; 07-12-9-964-675; -058; -716; -087; -096; 18-11-4-090-251.   6KT MU  M-8.  **NOTE that 07-12-9-922-058 is listed above for M-8 AND M-6...ONE is in error!

07-12-9-922-435; -434.  M-10.  self locking.
07-11-9-921-615; 07-11-9-900-079.    M-10 x 1.
07-11-9-922-148; -940; 07-11-9-921-627.   M12 x 1.5.
07-11-9-921-069; 07-11-9-901-307.   M 16 x 1.5.

Cap nuts (sometimes called closed dome nuts):
07-11-9-924-000  M-5
46-61-1-236-388; 07-11-9-924-403  M6
07-11-9-924-324  M-6
07-11-9-924-334  M-8
11-12-0-023-160; 11-12-1-744-330   for center of valve cover 


Lock & wave (spring) washers:  BMW has interchanged these at times per #, & I believe that sometimes BMW is not accurate on what type is which, as far as waverly, plain, locking.
07-11-9-932-009   A-3
07-11-9-932-013   B 3
07-11-9-932-030; -033  B-4 waverly.  'dented' washer is 07-11-9-936-041; -042
07-11-9-936-041   J 4.3  STAR washer   (note conflict with above line!)
07-11-9-932-041; -043  A-5   -041 replaced by -098; -043 by -047
07-11-9-932-079;   07-11-9-933-095  A-8
07-11-9-932-046   B-5 lock (spring washer, 5 x 11)
07-11-9-932-062; -061; -070; -071; -072;    #6  or B-6 
07-11-9-932-073   WAVERLY B6           
07-11-9-933-082   M-6 lock  may be error, may be flat washer
07-11-9-932-094;-093; -077   B-8 spring/waverly.  Book is unclear.  It appears that -094 is replaced by 07-11-9-932-079 which was replaced by 07-11-9-933-095, but -933-079.   I suspect a digit error on the -933- term.  07-11-9-933-095; -079   B-8 or M-8 lock (may be waverly).
07-11-9-932-112   B-10 spring;  may be A; large O.D.; for medium diameter A-10 use -103 and -111; for large O.D. A10 use -122. See also  07-11-1- 242-296.
07-11-9-933-110   B-10 lock.
07-11-9-936-042  J type 4.3 star washer.
21-21-1-242-377  A 7.4 star washer (BMW calls it a fan washer); clutch washers.
07-11-9-936-191  A 8.2 star washer. 
07-11-9-930-840  B8 SPLIT lockwasher.  This is the washer that was used at the driveshaft U-joint before BMW wised up & eliminated it in favor of a slightly shorter bolt.
34-11-1-240-570  flat size 8 washer 

Plain washers:
07-11-9-931-029  black
07-11-9-936-405; 07-11-9-931-622; 07-11-9-931-015   3.2
07-11-9-931-033; -030; 07-11-9-936-415; -416   A 5.3
07-11-9-931-065; -660; 07-11-9-932-081; 07-11-9-936-432   A 8.4 or plain 8.4
07-11-9-931-826; -684 for M8 bolts ; 8.4 
07-11-9-931-027   A4.3
07-11-9-931-043; -018; -650; -696; 34-21-4-044-133;  07-11-9-936-426; -408; -425   6.4  for M6 bolts 
07-11-9-931-668; -664; -649; -077; -698; 36-31-1-451-479    10.5    A 10.5
36-31-3-004-378   Thick washer for rear axle of /5; also see 33-41-1-232-709 and 33-17-1-236-956 for some or all later models.
07-11-9-931-083  A-13, used on size 12 bolts

Plain (solid) sealing washers & crush washers:

Note that many early crush type washers are now being shipped as slightly different number and are solid types.  This has happened with both aluminum and copper types.

07-11-9-963-140; -130  DT RG C  12 x 15.5 crush, driveshaft drain and driveshaft fill.
07-11-9-963-999; -470; -047; -041;    DT RG C (or A)    8 x 11.5   Fork drain, late model rear drive oil level inspection hole.
07-11-9-963-213; -200  14 x 20 DT RG  rear drive drain; transmission fill and drain.
07-11-9-963-259; -200   oversize  16 x 20 DT RG rear drive drain;  transmission fill and drain.
07-11-9-963-252   DT RG A 16 x 20   used at pulse air fitting at cylinder head and at the airbox.
07-11-9-963-073   10 x 13.5 x 1  solid washer for top of fork bolt.
07-11-9-931-622; -015   3.2
13-11-1-259-870   3.5 mm hole washer used on the Bing carburetor vacuum port screw.
07-11-9-936-413; -412;  07-11-9-931-637      A4 flat washer, 4.3
07-11-9-936-415; -416    5.3
07-11-9-963-010    DT RG A  5 x 7.5  small solid washer, fork drain.
07-11-9-963-151   solid washer 12 x 17  fork bottom.
07-11-9-963-034   solid washer, thermostat lower bolt  6.5 x 9.5.

07-11-9-963-130   DT RG A   12 x 15.5   solid washer for oil cooler banjo bolt; also at the neutral switch on early 5 speed transmissions.  see also 61-21-1-355-262, and at fork lower, bottom, center bolt. 
Here is further information on possible washers for the oil cooler banjo bolts:
07-11-9-963-151, A12 x 17-cu    These are copper, and note the 17 mm outer diameter.
07-11-9-963-132, A12 x 16-cu    These are copper, and note the 16 mm outer diameter.
07-11-9-963-130, A12 x 15, 5al   These are the stock aluminum washers, note the 15 mm outer diameter.

07-11-9-963-310; -300  DT RG C  18 x 22   crush, engine oil pan drain.  -300 is solid washer.
07-11-9-963-002   flat washer 3.5 x 6
07-11-9-963-420    DT RG  26 x 31  used at dipsticks until 1980.  Part is obsolete, but UNconfirmed information was that POSSIBLY #11-43-1-337-308 will work.

M-4 hex head bolts,  6KT SHR:
07-11-9-913-091    4 x 20
07-11-9-913-097    4 x 25 

M-5 hex head bolts:
6KT SHR 07-11-9-913-212   5 x 8
07-11-9-913-218   5 x 10
07-11-9-919-613   5 x 12
07-11-9-919-903; 07-11-9-913-252   5 x 20 

M-6 hex head bolts  6KT SHR
07-11-9-913-426; -432; 07-11-9-914-148    6 x 10
07-11-9-913-441; -014    6 x 12
07-11-9-913-451   M 6 x 14
07-11-9-913-465; -015; -464; -466; 07-11-9-911-218   M6 x 16
07-11-9-913-470; -019    6 x 18
07-11-9-913-476; -016;  07-11-9-915-030; 07-11-9-913-114   M6 x 20
07-11-9-913-567    6 x 22   
07-11-9-913-480; -018    6 x 25
31-42-1-240-053    6 x 28
07-11-9-913-499    6 x 28, could be 30 mm
31-42-1-237-529; 32-71-1-240-053; 07-11-9-913-590; 31-42-1-240-053; 07-11-9-913-573    6 x 30
07-11-9-912-303; 07-11-9-901-189    M6 x 35
07-11-9-912-312; -323    6 x 40
07-11-9-912-326; -324    6 x 45
07-11-9-912-335; -337    6 x 50
07-11-9-912-360    6 x 65 


M-8 hex head bolts  6KT SHR:
07-11-9-911-605; 07-11-9-910-342    8 x 12      thread pitch 1.0 
07-11-9-913-618; -624; 07-11-9-901-191; 07-11-9-919-939    8 x 16
07-11-9-913-640; 07-11-9-901-120   8 x 20
07-11-9-913-652   8 x 22
07-11-9-913-656; 07-11-9-901-125   M8 x 25
63-12-1-356-921   8 x 25   as used on side of /5 headlight shell
07-11-9-913-662   8 x 30
07-11-9-913-111; -674; 07-11-9-912-477; 33-41-1-232-701   M8 x 35
07-11-9-912-507   8 x 45 
07-11-9-918-655   8 x 50
07-11-9-912-556   8 x 80

M-10 hex head bolts:
07-11-9-911-631   10 x 1 x 20  as used with /5/6 oil filter inner cap
46-52-1-235-511   10 x 20 special shoulder bolt used at center stand
07-11-9-913-807   10 x 12
07-11-9-913-831; 07-11-9-913-834   10 x 25
07-11-9-913-839; 07-11-9-901-166   10 x 30
07-11-9-913-837; -844; 46-71-232-703     10 x 35   -837 may be 10 x 30
07-11-9-913-855; -853; -868; 07-11-9-901-169; 33-53-1-232-702   10 x 45
07-11-9-913-859   10 x 50
07-11-9-912-453; 07-11-9-919-756; 07-11-9-901-107   10 x 60 

M-12 hex head bolts:

M-14 hex head bolts:

4 mm Allen bolts  ZYL SHR:

07-11-9-919-381    4 x 12

5 mm Allen bolts  ZYL SHR:
07-11-9-919-611; 12-13-2-322-416    5 x 8
07-11-9-919-614; 07-11-9-900-311    M5 x 16
07-11-9-919-617; -903; 12-31-2-322-418    5 x 20
07-11-9-919-619    5 x 30
07-11-9-919-908; 12-31-2-322-417    5 x 45 

6 mm Allen bolts  ZYL SHR:
07-11-9-919-910   6 x 10
07-11-9-919-792   M6 x 10, with captive waverly
07-11-9-919-912   6 x 12  
07-11-9-919-621; -965; -913; -912   6 x 16
07-11-9-919-918; 46-54-2-322-498   M6 x 18
07-11-9-919-716; -920; 23-11-2-322-407    6 x 20   The -407 usually has a deep head which is particularly nice for use at the oil filter outer cover/housing.
07-11-9-919-921; 46-71-2-322-405; 07-11-9-919-625   M6 x 25
07-11-9-919-927; 31-42-2-311-105   6 x 30
07-11-9-919-931; -932   M6 x 35
07-11-9-919-937; 46-61-2-322-494    6 x 40
07-11-9-919-630   6 x 50
07-11-9-919-956; 61-12-2-322-496   6 x 60

8 mm Allen bolts  ZYL SHR:

07-11-9-919-637   8 x 12
07-11-9-919-640; 07-11-9-901-023   8 x 16  some books say 8 x 15 for -640
07-11-9-919-974; -969; 07-11-9-920-151   8 x 20      -974 may be 22 mm 
07-11-9-919-646; 07-11-9-901-024   8 x 25
07-11-9-919-647; 07-11-9-901-025   8 x 30
07-11-9-919-984; 07-11-9-901-027   8 x 35
07-11-9-919-648; 07-11-9-901-029   8 x 40
07-11-9-919-638; 07-11-9-901-033   8 x 45
07-11-9-919-649; -796; -803; 07-11-9-901-034   8 x 50     -034 may be 8 x 45
07-11-9-919-651   8 x 55
07-11-9-919-656; 07-11-9-901-036   8 x 80 


10 mm Allen bolts:
07-11-9-919-662   M10 x 12
07-11-9-919-787; 07-11-9-901-039   10 x 20
07-11-9-919-769; 07-11-9-901-049   10 x 30
07-11-9-919-740; -771; 07-11-9-901-064   10 x 35
07-11-9-919-756; 07-11-9-901-107   10 x 40   may be error, -107 may be 60 mm long
07-11-9-919-672; 33-17-1-454-309; 07-11-9-901-088   10 x 45
07-11-9-919-739   10 x 50 

12 mm Allen bolts ZYL  SHR:
The only 12 mm "fillister head" (totally different head than the American slotted head called a fillister as BMW calls it) that I remember is 07-11-9-901-116, which is M12 x 40, used at the bottom center of the forks of the R100RS, R100RT, R80RT, up into late 1984 (??)  ....and the R65GS and R80GS, not sure of years....and the last use that I know about is as a frame bolt in the R1100S.  Basically, used on many forks at the bottom center of the slider.  A 30 mm length version was 07-11-9-919-766, superceded by 07-11-9-919-778.

14 mm Allen bolts


Threaded lengths, studs:
07-11-9-908-255   STI SHR   6 x 25
07-11-9-908-104   STI SHR   6 x 40

07-11-9-908-378   10 x 50, used at 12:00 and 6:00 on cylinders-to-head.  This number is no longer valid....because, there seems to be two others involved now:  07-12-9-908-174; may be 07-11-9-908-174 in some books, or, may be two types of these with different numbers!  M10 x 30 in some old literature, yet latest fiche says M10 x 50. Used on cylinders-to-head.   It is obvious that there is confusion over these three above numbers.

11-11-1-252-310   STI SHR   length??   used at front of engine-to-timing chest
07-11-9-903-306   STI SHR   8 x 18
07-12-9-903-326   STI SHR   8 x 25
07-11-9-903-349; 07-12-9-908-130   STI SHR   M8 x 35
07-12-9-908-141   STI SHR   8 x 45
07-12-9-908-135   STI SHR   M8 x 50
07-12-9-908-137   STI SHR   8 x 55
07-12-9-908-145   STI SHR   8 x 65 mm ...the original valve cover center stud. 
07-12-9-908-142,  STI  SHR  8 x 70 mm...longer version of the valve cover center stud.
07-11-9-908-385;    STI SHR M 10 x 35  SN 4
07-11-9-903-436   obsolete number for a stud.  Can't find my information on it at present.
07-11-9-908-391   Appears to be an obsolete part number; replaced by 07-12-9-908-177.  That number may or may not be available.  It is called out as 10 x 55 in some literature.  Used at the rear drive for the shock mounting, /5 to at least into the eighties.  A very strong rating would seem to be a must for this part.  I suspect it is specified at 10.9 (??). I have not had a chance to remove a proper one from a rear drive MYSELF for testing.   From what has been reported to me, is likely a DIN 835 M10 x 55; a special stud specification.  This stud measures 20 mm long on the end that fits into the rear drive.  The NUT end is 26 mm.  The overall length is 75 mm.  The length of the nut end and the UNthreaded portion is 55mm. This is NOT a common hardware store stud item. This type of stud is mandatory for such a high stress position.  Use heat when trying to remove one. May be:   Din 835 M10 x 55, available from; but strength rating seems low.  Metric & Multistandard Components Corp.

11-11-1-257-397   275 mm cylinder stud, 10 x 1.5 mm
11-11-1-265-195   297 mm cylinder stud; used at right side, rear, both, 10 x 1.5 mm.  This longer cylinder stud is used on the RIGHT side cylinder, top and bottom rear.
46-71-1-230-475; -762  long threaded at both ends studs used at footrest   M12 x 1.5
46-71-1-230-762, engine mount stud, 306 mm long
46-71-2-311-725, engine mount stud, 315 mm long
46-71-1-230-475, engine mount stud, 327 mm long

Common (??) screws, can be slotted or phillips, EVEN IF codes say other type
07-11-9-907-701   special screw used at fairing vents, really a size 3, but book says B2.9 x 6.5.
07-11-9-928-432; -130; -103   M4 x 16   SK SHR, screw used at fairing vents.
07-11-9-907-603   3 x 10  LIN SHR  see next line.
07-11-9-907-602   LIN SHR AM 3 x 8 screw used at one style of crankcase oil breather; NOTE:  book shows -602 to be used for -603.
07-11-9-907-604   LIN SHR AM 3 x 10.
07-11-9-907-616   LIN SHR AM 4 x 10.
07-11-9-906-435   LIN SHR 4 X 12.
07-11-9-913-373   4 x 10  ZYL SHR AM.
07-11-9-919-381   4 x 12  ZYL SHR AM.
07-11-9-901-703   4 x 12  LIN SK SHR.
07-11-9-901-720; 07-11-9-928-439   SHR AM 4 x 20  phillips.
07-11-9-907-639   LIN SHR 5 x 10  used at seat side rail.
07-11-9-907-627   LIN SHR AM 5 x 12.
07-11-9-901-771   5 x 15  LIN SK SHR AM.
07-11-9-906-415   SHR AM  5 x 16.
07-11-9-928-485; -487; -488   5 x 15  LIN SK SHR M    replacements are 5 x 20.
07-11-9-901-771   LIN SK SHR  5 x 15  used at the seat strap.
07-11-9-907-631; -633   5 x 20  LIN SHR AM.
07-11-9-900-810   SK SHR M 6 X 10   counter sunk allen head used at seat hinge.
46-63-1-236-414   SHR M6 x 30.

Miscl. hardware:

If the flywheel has a groove (and it will if it is 10/1975 or later), it needs an o-ring there. It was 11-22-1-337-099, now is -093.  A long time ago the number was 11-22-1-263-798.  The O-ring is called a Seal Ring by BMW.  It is 59 mm x 3 mm.

51-14-4-034-136:  This is the frame ID metal plate, comes flat, you must curve it, it fits the steering head area, is designed to be riveted in place.   These are NOT obtainable from BMW, AFAIK.  Bob's BMW has them, you have to stamp in your model, serial, etc.

Fairing pocket rubber channel material: it fits between fairing pockets and the fairing.   Many have substituted part 05-01300 #1 Rubber Channel; from   It has a 1/16" groove and is 3/4" high.  Can also be used at the pockets themselves, where the covers fit.

Fairing pocket COVERS: 
These use solid, soft, round rubber strips that many folks install with cyanoacrylic cement (Crazy Glue, etc).  That 'glue' may NOT hold up.   Unfortunately, many times this rubber is not thick enough for one's particular covers & fairing pockets, & there are water leaks, rattles, etc.  If you go to Lowe's, or Home Depot, etc., you can find, quite cheaply (compared to BMW price for the too small strips) 'gasket' material, made of a rubber compound, and it has a splined-look.  It is found in the area of the store that has screen doors & hardware for screen doors.  Smallest package I've seen is 25 feet, for a few dollars.  I have seen this stuff in various sizes, from 0.110" thick to 0.175" thick.   I use Elmers Probond to install it, using very light clamping pressure.  It dries quickly enough, but not spectacularly quickly. After it dries overnight, I apply a second dab here and there to be sure the adhesion is very strong. The stock gasketing material from BMW is 46-63-1-239-586, one piece, 485 mm in length.

Rubber seal-strip (or rubber O-ring, whatever you want to call it), located in the PRE-1979 timing chest, in a groove, surrounding the points cavity,
has two part numbers in the books: 
These come in lengths you cut to fit.  Install them after cleaning them with acetone, & clean the cavity for them quite well too.  Put small droplets of cyano-acrylic glue (Crazy Glue, etc.) in the cavity groove, before installing.   Push a few times into position if need-be.  Cut with an Xacto knife to fit; let sit overnight.  NEXT; CLEAN with acetone.  I do NOT recommend what others have, which is to rub with a bar of soap as the next step after the acetone cleaning.   I smear a VERY SMALL amount of silicone dielectric grease on the surface, using my finger,
before replacing the outer cover.
11-14-1-265-394 is supposedly 3.2 mm, used until 1974.
11-14-1-262-644 is supposedly 4.2 mm, used after 1974.
If you were to order either, you probably will get just 394 size.  Maybe.
You can use a Classic K bike oil filter cover O-ring, which is 11-13-1-460-425, even a used one!  Thanks to Tom Cutter, for this hint!

The Classic K bikes are K1, K75, K100, K1100.

BMW has a SEAL available to block off the mechanical tachometer takeoff area.  The worm, etc., at the engine case, can be left in place. The seal is 63-23-1-351-257. 

61-12-2-302-574   solid, better construction, flip-cap cover for the electrical accessory socket.   This is a K bike part that fits.

46-31-1-244-384   UNconfirmed number for a blank plug to fill the RT/RS large round dash holes when no voltmeter or clock.
11-11-1-744-327   black rubber timing hole plug.

61-21-1-230-392   black rubber battery strap for /5 & later.  The -392, brand-new, was measured & reported to me as being 26.41 cm (10.4") from center to center of the pins, which were 0.2" in diameter.
61-21-1-243-562   black rubber battery strap for R65, R80G/S, R80ST, and some few others.       Dimensions:  ???

Dual stud mounts, black rubber, as used at battery bracket, fuel tank, diode board, ETC:
These are getting very pricey from BMW.   Try this link, which has both American and metric threaded items, vastly cheaper...and even has type with single studs, ETC.  I recommend you do NOT replace rubber types if they came that way at the diode board, but, install solid metal aftermarket types.

46-51-1-234-785   black plastic cover for hex head of M8 bolts.

52-53-1-452-295   metal seat post with notches.  This is the notched locking post that screws into the seat pan.  It is for some 1984, & many 1985 and later bikes.  It may fit the earlier bikes, or can be made to fit.  Because of the very high price, & that I am not sure that part will fit earlier bikes, I am recommending that you obtain the part from  Search that website for part   91900S.
52-53-1-230-313   black rubber bumper used over the seat locking rod, that fits into the seat lock
52-53-1-232-904   round bumper with attaching tit, used at the seats.
07-12-9-934-318   special type of C clip used to hold seat to right frame rail pegs. D6,0

61-31-8-050-134; 63-12-1-244-378   Chrome washer, side of /5 headlight shell.
61-31-8-050-136   rubber washer used with above Chrome washer.
61-13-8-050-138   rubber sleeve used with above two items.

46-51-1-231-233   Oversize peg that is pressed into the frame for the sidestand.  The frame is to be reamed for an interference fit.
46-52-1-236-528   11 mm bushing used in /7 & later center-stands (to 9/80).  Used with a flathead bolt 10  x 1.5.
46-52-2-301-704   Oversize bushing for center-stands, it is 13.5 mm and uses M12 x 30 bolt.

(are measured from hook end to hook end...the length is the maximum over-all length, NOT stretched).
46-52-1-234-514    xx mm center-stand spring.  NO information yet on length
46-52-1-236-282   97 mm center-stand spring
46-52-2-331-805   111 mm center-stand spring
46-52-2-301-583   143 mm center-stand spring

Source for automatic advance springs:


No specific section, just "stuff":
46-63-1-235-759   closed end tube-grommet/rubber/plastic? cover fairing screw sharp tips.
46-63-1-235-760   B 4.2-4BL MU  BMW's version of Tinnerman nut for fairings.  Number has been replaced by 07-12-9-904-144.      This part can be listed in the catalogs in various ways, including BLMU and BL MU 4,2-4.
07-11-9-902-513   BL SHR BZ 4.2 x 19   the screw used with those Tinnerman's, above....there is a short  version   4.2 x 16   #07-11-9-902-514 which is replaced by -497.
46-63-1-235-510   cup washer for fairing taper head sheet metal screws.
46-63-1-235-512   screw used in joining sections of the fairing on RS and RT models.
07-11-9-907-944; -946   LIN BL SHR BZ 4.2 x 13  another of the screws used with the Tinnerman's.
07-11-9-902-467; -468  black phillips head sheet metal screw.
07-11-9-902-441   silver colored phillips head sheet metal screw 3.5 x 16.
07-12-9-948-739   3.2  rivet.
07-11-9-947-201   6 x 25 rivet.
46-63-1-233-909   expandable rivet used at windshield.
07-11-9-949-633   A 6 x 0.4 x 10 tubular rivet used at top of fairing area.
07-11-9-902-429   phillips screw 3.5 x 16  used at fairing rubber tunnel; replaced by -441.
21-21-1-231-463   ZYL SHR  special bolt for clutch.  Note that except for the R46 and R65 which use a smaller bolt, BMW changed from an early slot screw to Allen style.  #'s for these bolts have been  -463, and 21-21-1-242-371 and 21-21-338-680.

26-11-1-230-414   special 12 point bolt, M8 x 14.5 for U-joint, original early type that used actual split style lockwasher B-8  07-11-9-930-840.   ALWAYS replaced these with the shorter 13 mm length bolt withOUT that washer (26-11-1-242-297).

33-53-3-054-174   27 mm thin nut used at the swing arm.

13-11-1-259-869   screw for Bing vacuum takeoff tube; -870 is the washer.  The screw is 3.5 mm x 0.6 pitch.
13-11-1-337-361   screw for Bing CV carburetor tops.  LIN SK SHR.  Fillister head (tapered) M5 x 0.8 pitch, 12 mm long.  Always use a faint amount of antiseize compound on the threads AND under the head.

13-11-1-336-900   METAL fuel T fitting.
11-12-1-337-818   rubber pads used for quieting the cylinder head fins.

71-60-9-024-186   U shaped bolt used at cylinder crash bars, size 8 threads.
46-71-1-230-794; 46-71-1-237-759   U shaped flat clamp with one threaded end, used at cylinder crash bars, size 8 threads.  The ABOVE THREE bolt/clamp units are used on the large SINGLE crash bar that covers both sides on the early airheads.   There is a single type, one for left, one for right, and the clamp is 46-71-1-235-772 in chrome (now 46-71-1-230-794) and 46-71-1-237-759 in dull black.

FRONT FORK, controls assemblies, ETC: 
The headlight fork tube ears, at the TOP, just under the top triple clamp, have a rubber bushing...a sort of rubber O-ring.  FOUR sizes were need to use the one that fits properly on your bike.
31-42-1-232-527  is 3 mm thick.
31-42-1-230-696  is 4 mm thick.
31-42-1-230-697  is 5 mm thick.
31-42-1-230-698  is 6 mm thick.
There is also a rubber bushing or O-ring, located at the BOTTOM of the headlight ears; which is ONLY of one type and part number:  31-42-2-000-385.

Throttle friction device:  This is a special screw, all-metal (except for nylon friction tip), threaded 8mm x 0.75 mm, with a 'sort-of' captive spring.   The primary usage was originally for setting the throttle, for such as adjusting the carburetors; but a secondary purpose was to relieve some right hand stress.   It has been, over the years, on various models at various times.  Sometimes the throttle assembly was not drilled or not drilled/tapped for them. There are some variances, and the part numbers for the knurled screw with its spring (the knurled screw has a nylon or similar hard plastic tip, which works nicely against the throttle tube), are:
K bikes and R80R and R100R:  32-72-1-454-414. 
Rest of the Airheads:  32-72-1-230-874.  Shorter than the above one.

The blanking plug was 32-72-1-236-605, probably fits all of those bikes (?).



Steering head: 
The steering head bearing is common type 32028, 28 x 52 x 16 mm.  BMW has used this number on all the Airheads, and even the Classic K-bikes.  BMW dealerships have all sorts of prices for that bearing.   There are variations on the 32028 part number, you may find 320/28X and others.  The bearing may be listed as I.D. 1.102"; O.D. 2.047"; width as 16 mm.     You can purchase this bearing almost anyplace, even a local autoparts store, which MIGHT list it as a A-32 bearing.   Just ask for a tapered roller bearing, and provide these numbers.  Prices will be MUCH cheaper than many BMW dealerships ask.  Do NOT ask for any special tolerance.

Swing arm and wheel bearings:
The swing arm bearings are 30203A, 17 x 40 x 12 mm; and are basically the same as MOST of the pre-1985 wheel bearings, which are 30203.  The difference is sealed versus unsealed. I like them UNsealed, at both places.  The swing arm bearings, unsealed, grease very nicely from the hex hole in the swing arm pins.  Every few years I remove the entire rear end on my own Airheads, and hand clean those swing arm bearings.  A REALLY good time to do that is when removing the transmission for a THOROUGH transmission input spline cleaning and lubricating...or other work, such as on the clutch, etc.     If I am working on a bike and find sealed bearings at the swing arms, I puncture the seal, or remove the seal, so I can get proper greasing in the future from and into the 6 mm Allen adjuster hole.  For the wheel bearings, they are to be lubricated every other tire change.

My comments for the steering head bearings pricing and where to buy, above, ALSO APPLY to the swing arm bearings & wheel bearings.


Crankcase breather, disc style was on the early Airheads;  later was a reed valve.  The disc is ~1/16" thick, 27 mm diameter 0.22" (#2 drill) hole if you want to make one.  Printed circuit board of fiberglass material is OK for this.  Source for newly made old-style Airhead breather discs, $5 each, $4 for O-rings, including USPS shipping:  Dave Thompson,

Hearsay has it that a better O-ring for the VM clock is the Harley Davidson oil pump cover O-ring  #26434-76.

Valve stems for tubeless tires/rims:
I use two types of valve stems on BMW bikes:
The part numbers, details, are from MEMORY, so one should double check me here before ordering any.  36-32-1-452-748 is the kit consisting of the metal (steel) valve stem with O-ring and valve cap and nut. Nicely made product.  These are used with Airhead tubeless rims as well as the cast K bike rims.  For spoke wheels I use these with an 8 mm flat washer  07-11-9-931-697, which IS specified for their use.  There is a 1-1/4"  chrome valve stem, on a 45 degree angle, that I have used on the cast Snowflake rims.  0.435" holes, that I get from, part 17-561, has a special inner grommet.

Long lasting fuel hose:

Rubber seal for the screw-in gas caps (NOT the black trim ring, but the SEAL, originally RED, but the red ones broke after awhile):  51-25-1-453-148.
The black trim ring is 16-11-2-307-360.  This is NOT a seal, but a trim piece; it also helps keep rain from getting into the 'shelf' of the tank under the cap (where a drain hole is).

23-13-1-241-484   special clutch arm (at rear of transmission) PIN.  This pin that has a flange, and won't fly out.  This is used with a clip that is 51-23-1-864-963.    These two parts replace an earlier pin that uses a C clip.  That early version sometimes lost the C-clip, due to being improperly assembled, and then a transmission ear got broken off.

11-13-0-007-163; 11-13-1-744-329   magnetic drain plug used at transmission.
11-13-0-007-162   oversize magnetic drain plug used at transmission and rear drive; believe is used with oversize gasket-washer 07-11-9-963-259.  Original size 14 x 18 mm; larger was 16 x 20 mm.

Drain plugs and their crush washers are available in oversizes.   Example:  The standard rear drive plug is 11-13-0-007-163; oversize is 11-13-0-007-162; standard crush washer is 14 x 18    #07-11-9-963-213 and the oversize is 16 x 20  #07-11-9-963-259.
11-41-2-343-498   magnetic drain plug....not Airhead.  Used on some F650 models.  M18 x 1.5.  Used with washer 11-31-2-343-091.

23-11-1-230-599   hollow breather bolt used at transmission speedometer cable and battery.
07-11-9-905-660   special set screw, MAY have slot,  M4 x 6 x 3,   neutral switch on /5.
07-11-9-941-332   3 x 18 roll pin.
07-11-9-944-651   4 x 10 roll pin.
07-11-9-941-471   5 x 50 roll pin.
07-11-9-941-475; 07-11-9-941-470   5 x 60 roll pin.
07-11-9-941-485   6 x 16 roll pin.

11-42-1-335-394   Special 23 mm bolt for filling thermostat/cooler.  Do NOT use if longer than 23 mm! Some wrong length ones were provided by BMW!   Photo of correct one & wrong one, is below.  If you were to measure these, they vary a bit from 23 & 30 mm....but not too much.    Note that the threaded ends are rounded, that does not show up well in these photos.   Typically you would find the "23mm" bolt to measure about 0.918" from under the hex to the tip; and the "30mm" one might be 1.184".

16-11-1-232-237   plastic washer that fits 4 mm screws.
16-12-1-240-513   16 x 2 rubber O-ring.

Neutral switch for 5 speed transmissions; and, the spacer:
  The STOCK 1974-1975  5 speed transmissions use neutral switch 61-31-1-352-153.  If you have the shift kit installed, or you have a 1976 & later transmission, you use switch 61-31-1-243-097.  For the -097 switch you must use ONE special washer, which is 61-31-1-355-262.  DO NOT use a common drain plug gasket washer!   Reports of BMW shipping the wrong washer have been seen.   Tom Cutter measured a new one & it was 19.8 mm x 12.35 mm x 1.89 mm.  Original new ones, which might fit better (?) are probably 2.0 mm thick.  It is best to use a new washer, but sometimes the old one will seal adequately.

61-31-1-243-454   Rocker switch, with cable; switch snaps into the place in the dash meant for it.

07-11-9-987-611   Lock bow clip.  This thin question-mark-shaped round steel WIRE is used to lock the balls at the shift linkage and the hydraulic damper balls.

36-11-2-227-943  wheel weights, 5 and 10 gm segments, stick-on, used on R1200C, etc.

61-13-8-080-160   Rubber boot for the speedometer cable where cable fits the right side rear of the transmission


BMW uses various spacers that I call "top hat spacers".  BMW calls them Thrust Sleeves.  A top hat spacer is a tubular thin-walled spacer made of metal, with a brim on one end.   In airheads prior to 1985, on twin shock models, at the rear wheel, these are used to space the wheel the appropriate distance in the swing arm.  They are also used on front wheels. They are also used in the swing arm to space it in the frame.  These top hat spacers GENERALLY fit FROM inside the rubber seal, with a couple of exceptions.    These top hat spacers (thrust sleeves) ARE NOT the many-sizes-available thick small 'preload' spacer that do NOT have a HAT, and are often called the Wedding Ring, and are used in pre-1985 wheel hubs to space the tapered roller bearings. 
36-31-4-038-142:  This spacer is the stock one, it is typically 0.359" wide (height, usually with slight variances seen) fact I have seen them from 9.0 to 9.2 mm. 

It is common to see the stock right side top hat spacer replaced by the 10.7 mm wide one, 36-31-2-301-737, that BMW offers just for moving the rear wheel over slightly to the left (especially pre-1982), to allow a wider rear tire.  Once in awhile an even wider spacer is used: 36-31-230-322:  This top hat spacer was made in two styles with the SAME part number!   BOTH have a width (height) of 12.9 to 13 mm.  An early version was extra wide on the top hat portion...a diameter of 31.95 mm nominally.  The "seal' surface of this spacer measures an O.D. of 21.95 mm.     Information on using top hat & other spacers for the wheels is found in articles on the wheels on this site.  Sometimes one must add flat spacers or move rear disc brake arm slightly, etc., when dealing with certain types of tires.

BMW 71-11-1-103-086  Screwdriver; Phillips & Pozi-driv & Reed & Prince screws (see TOOLS article for lots more info):

The BMW screwdriver with the red plastic handle that comes in the Airhead tool kit from BMW has a standard Phillips shaped-tip, which removes/reverses... and there is a flat type tip on the other end. NEITHER is made all that well.  This screwdriver does NOT have a Pozi or Reed & Prince type of tip.    

Bing carburetor top "Phillips" screws may not really be Phillips screws, they MAY just look like one at a quick glance. They could be Phillips...or... could be 'Pozi' type, or a bastardized version of the Japanese type.  The ancient aircraft tip called Reed & Prince (Frearson) works OK on the Pozi, of course, does the real Pozi. 
The Pozi-tipped screwdriver is EXCELLENT for REMOVING the Phillips type, if the Phillips is quite tight.  

Install carb screws with anti-seize compound on the threads AND ON THE TAPER.

Japanese  JIS B 1012:   These are different, but look like Phillips screws, & CAN be used with a Phillips screwdriver.  These screws are identified by a single dot or a tiny x, on the head.

For a much more complete treatment of these, AND various other screw heads:

If the carburetor top screws are frozen, you can try a variety of ideas, see my carb articles.  This includes valve grinding compound for a better grip, a metal block underneath and an Impakt Driver, etc.   Tips for interchangeable-tip type tools are available from a variety of sources, including Snap-On. YES, the Pozi IS available.    The only critical 'Phillips' (appearing to be) type screw place on our Airheads is the screws used on the top of the Bing CV carburetors....although some would argue for the screw that holds the pod umbilical cord to the pod, but the problem there is just over-tightening, not removal.   Some have installed Allen head screws at the carb tops.  That is OK, but don't over-tighten, as many of these have a very small allen size; can round-out more easily.  I DISLIKE Allen's there.    Some early Bing carburetors CAME with common single slot screws.    Bing has shipped BOTH Pozi & Phillips screws on later sure that your 'screwdriver' fits them PROPERLY, & do obtain a Pozi #2 or Reed & Prince screwdriver or tip.  Remove the screws one at a time, coat the threads...and taper...with antiseize....replace the will appreciate this hint, later on.

Real Pozidriv screws have some radiating lines to indicate they are not Phillips type.

Little known facts:   Phillips screws & screwdrivers were NOT DESIGNED to prevent over-torquing; that is, they were NOT designed so the screwdriver would SLIP after a certain amount of torque is applied.  That came about as tooling got worn.  Because of the specific design of the side tines of the Phillips, one needs different sizes of screwdrivers, as the wrong size will NOT FIT CORRECTLY.

Here are photos of the
Pozi-Driv screw, and the screwdriver tip.  Note the differences from your Phillips!

 See  for more on the Phillips/Pozi and the Reed and Prince (Frearson).  For a much more complete treatment of these, AND various other screw heads:

Discussion of 'locking' methods for hardware:

In general, the most basic reason for having screw & bolt threads is to prevent something from loosening.   One of several more reasons is to maintain a specific clamping force between parts.  These parts could be brake caliper halves; a bolt holding a bracket to a casting; or any of many millions of clamping and other reasons.  I am sure you learned NOTHING from that paragraph.

But, almost every person, including some with degrees in mechanical engineering, do NOT have information about how a simple screw or bolt or same with a nut, actually works.   This can become a safety issue, if you substitute something where the factory had specific reasons for something...or; many other things could be discussed here.

The actual holding forces in most fittings/fitments... is NOT the forces in the threads from the clamping torque, but is the force under the head of the bolt (the clamping surfaces of the underside of the bolt or nut or the surface of the casting, etc.).   This is often hard for someone to understand.  The threads only enable the contacting forces to occur.....and to help maintain them.   A gross example of this is the alternator rotor in your Airhead, where two tapers, a male & female, provide all the holding force, once brought together by the central allen bolt.  It takes a considerable force, supplied by tightening quite highly a special bolt, to separate these pieces, once tightened, and original bolt removed.  Other examples might be where highly finished surfaces touch each other...very little clamping is needed to allow large forces.   I fully understand that this is a hard concept to get your brain around, particularly with common bolts holding flat surfaces together.

You do NOT want something to 'loosen' when you do not want it to; yet you want to be able to unfasten something when that is needed. 

Owning an Airhead, you are undoubtedly aware of a GOOF by BMW, when the company specified a split type of lockwasher for the 4 bolts that hold the driveshaft Universal Joint to the transmission output flange.  Split lockwashers are generally made of a hard material that has a quite modest amount of ability to distort (flatten), and usually the opening area of such lockwashers have sharp surfaces, which can dig into and thus grab the surfaces they come in contact with.  Some driveshaft U-joints became loose, disconnected/unfastened, and tore off the back of the transmission or caused other serious problems.   The split lockwasher was NOT the proper type of locking method. Think about what happens to that lockwasher as you tighten the bolt.  The lockwasher is under a lot of stress, it is somewhat brittle, and rotating the bolt can tend to try to not only flatten the lockwasher (which is already 'twisted' slightly), but the bolt might grab a raised edge of the lockwasher and actually try to expand the diameter of the lockwasher.  THINK ABOUT IT...AND LOOK AT A LOCKWASHER, SLIP ONE OVER A BOLT, AND CONSIDER HOW IT REALLY WORKS.

In fact, use of NO locking washer at all would have been FAR better!    THAT is what BMW recommend later.  NOTE that BMW made the updated bolts slightly shorter, as if the originals were used without lockwashers the bolt might be long enough to damage the seal behind the flange.  Those of us 'in the know' who use the NO lockwasher shorter bolt might also use a drop of a medium Loctite product, generally just called 'blue', cleaning the threads first.

Repetitive stresses & forces tend to loosen things.  It is actually fairly common in high forces areas that if something is even a teeny bit loose, intense LOOSENING AND BREAKING forces arise.  Very critical items can be such as wheel bolts/nuts; brake caliper mounting bolt & nut; or something very simple like a single small screw holding an electrical connection.

In some situations, tightening & clamping forces are EXTRA CRITICAL.   One such on the Monolever and Paralever Airheads is the REAR WHEEL BOLTS.  NEVER lubricate these items.  NEVER use antiseize compound on them either.  The wheel is aluminum alloy and expands and contracts much faster than the steel bolts.  BMW has a design method for those bolts, which are of a certain size and length and must be tightened to specifications, under which the proper tension is applied. Failure to properly install the bolts can result in an 'exciting' departure of the rear wheel from the motorcycle!

What should you know about methods of fastening things where mechanical stresses can occur (they CAN occur just from normal day to day temperature changes, not just mechanically induced stresses)?  Obviously, the more stress cycling there is, the more likely for a threaded fastener to loosen. Using numbers of stress cyclings (official terminology is number of load cycles), versus actual clamping load, the following is information you can trust:

1.  An UNsecured (no locking method) bolt & nut is generally the worst case...somewhat depending on materials, steel-into-aluminum?, steel-into-steel?  Strength drops quickly & constantly.  Similar, only a bit better, is a bolt with a split ring lock washer & a nut; & only a bit better than that is a bolt with a toothed type lock washer & a nut. In general, split and sometimes other types of lock-washers, are NOT appropriate where forces applied are irregular, or recurring.
2.  Next is an elastic stop nut.  The strength drops SOMEwhat quickly with load cycles...but then deteriorates only very slowly with additional cycles.  This is why this type of nut is used in more critical applications.
3.  Next is a bolt with the underside of its head being a saw-toothed flange.
4.  The best is usually a bolt that has the correct type of Loctite (or similar) product applied.
The difference between #3 and #4 can be small.  The difference between #1 and #2 and #3 or #4 is HUGE.

Initial upload:  02/25/2003
In general, specific updates/changes MAY not be identified here.
07/12/2016:  Major update. Clarity, layout, scripts, H.L., metacodes.  Quite a few changes to part numbers and descriptions.

Last check/edit: Monday, February 20, 2017

© Copyright, 2014, R. Fleischer

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Last check/edit: Monday, February 20, 2017