During the R246/7/8 production there were a few changes to the throttle systems that can complicate repairs and modifications. Roughly speaking, there are five types of throttle systems on these models:
Each of these has a unique housing, due to changes in the brake pull or the number of throttle cables, and a unique cover. The throttle cams changed for different models, and were upgraded at one point requiring new housing covers. Even the throttle tubes can be different. So, there are a lot of different parts and you need to know which parts go with which.
I wrote this page to help me identify some new but unbagged throttle components (mostly cams) that I had. I was ordering new cams for customer bikes and not fully understanding how they differed from those I already had, so I decided to investigate. In the process I also clarified which throttle assemblies were best for various modifications some of my customers were making.
'70 through '74 (32 72 1 232 464 and ?, 32 72 1 232 664 and cover 32 72 1 233 306). Double-pull, they can be recognized by the small size and the Hella switch mounts. Due to the small size, only the no-ramp throttle cam will fit inside. The housing and cover split in the middle of the lower cable holder. Housing is threaded for the barrel-type brake light switch. Early models had a shorter stalk where the cable entered; I'll add details as I can. This system has no parts in common with any other.
'75 through '80 (32 72 1 233 537 and cover 32 72 1 233 538). Larger, with a cable pull for the drum brake or the under-tank master cylinder, and the throttle cable pull goes straight across from the front edge of the housing. Like the previous one, the housing and cover split in the middle of the lower throttle cable holder. Threaded for the small brake switch (not used on all bikes).
'81 through '84 (32 72 1 242 563 and cover 32 72 1 457 050). Single pull, housing and cover split in the middle of the throttle cable holder. Housing is threaded for the small brake switch. The throttle cable pull is swept rearward compared to previous ones to allow room for the master cylinder in front. In some cases (like the G/S) this design was used past 1984.
|Slash 5 type housing shown with the only
throttle cam that fits
|'75 through '80 housing has a straight pull
and a brake cable
|'81-on housing has a swept-back pull
a bolt-on master cylinder (not shown).
'85-on (32 72 1 454 461 and cover 32 72 1 457 039). Nearly identical to the single-pull, but the housing and cover each have one full cable holder. Threaded for the larger brake switch.
Paralever Starting in '91, the GS and subsequent R100R and Mystik used the K-style housings. These were only available in single-pull, so boxers used an adapter to feed two throttle cables through the single hole. Regardless of the engine type, they all used the same throttle cam. Threaded for the large brake switch.
Early R65 There was also a double-pull 32 72 1 238 377 housing (NLA) and 32 72 1 238 379 cover used on the pre-'81 R65 that is NLA. That R65 used a special round master cylinder reservoir and a unique lever. If I get more details I'll add them.
'81 and later cams were upgraded to the larger 15mm hole, requiring an updated cover. Without this cover, the new cam will slip on the throttle tube. Old covers (for the cams with 8mm holes) are obsolete and NLA. '85-on covers are already 15mm.
|On the left is an old cover which takes the cam with the stepped 8mm hole. On the right you can see the post that is needed for all 15mm cams.|
Cams have two thicknesses, three different ramp profiles, single-pull or double-pull ends, and (in the case of the early single-pull ones) two different hole sizes.
|Here you can see the three different ramp profiles. From the left: no ramp, low ramp, high ramp.||Here you can see the two hole sizes: On the left is the new 15mm hole, and on the right is the older 8mm stepped hole.||On the left is an '81-on cam, and on the right is a pre-'81 cam where you can see the extra thickness between the teeth and the ramp. Also visible are the single-pull and double-pull ends.|
Worn cams (and their matching throttle tubes) are a common cause of throttle stiffness. Especially if you feel a notchiness in the throttle action, you need to replace the cam and throttle tube (which can get expensive with heated grips). If you have an '81~'84 bike with the old cover, you'll need to buy the new cover to match the upgraded cam you'll receive.
|single pull||double pull||Notes|
for cable brake
|no ramp||-||32 72 1 232 463||'70~'74
only one that will fit the /5 housing
|low ramp||-||32 72 1 233 535||'75~'80 32mm|
|high ramp||-||32 72 1 233 536||'75~'80 40mm|
for bar-mounted MC
|no ramp||32 72 1 457 080 (15mm)||
32 72 1 238 378 (8mm)
|low ramp||32 72 1 457 036 (15mm)||-||'81-on K-type switchgear
(32mm or 40mm)
|high ramp||32 72 1 457 081 (15mm)||32 72 1 458 092 (15mm)||'81-on 40m pm|
Note that the throttle tube is also different for '70~'74. The difference is that the retaining groove is a few millimeters closer to the teeth starting in '81. Using a later tube with that throttle assembly will not work because the teeth will barely be engaged.
Current part numbers:
'70~'74 - 32 72 1 233 307 - with black knurled Magura grip
'75-on - 32 72 1 454 129 - with gray lengthwise ribbed grip, closed-end. Includes '91-on GS, K75 and some K100 models.
R100R/M, some K100/LT/RT - 32 72 1 451 732 - open end?
|Double pull '88 GS||Single pull '82 R100|