BMW Driveshaft to transmission output flange fitting, all Airhead models:
The correct part number for bolts for all models is: 26 11 1 242 297
NOTE: Do NOT use a lock washer, even if yours came with one. Use only the bolts above. A drop of blue Loctite on each is a good idea. You need 4 bolts, and these should ALWAYS be replaced with new ones. Never reuse a bolt. These are designed to stretch a specific amount at the correct torque, and cannot be re-used (except in an emergency of course, but that's your decision!)
The correct tightening torque is WITH the BMW special adapter according to Haynes BMW Twins 1970-1988:
"NOTE: On all models the torque setting is specified to take into account the leverage which results from the use of the special crowsfoot type spanner BMW Tool 00.2.560; do NOT attempt to approximate it using any other means (such as applying a measured pull at the end of a spanner of known length). Use ONLY the BMW tool to tighten the bolts; if necessary take the machine to a BMW dealer..."
Torque settings according to "Haynes BMW Twins 1970-1988 Owners Workshop Manual":
BMW Models 1970-1988 | lb-ft | Nm |
/5 /6 - bolts 14.5 mm long | 18-19 | 24-26 |
R80, R80RT 1985 on - bolts 13.0 mm long | 23-29 | 31.6-39.6 |
All other models - bolts 13.0mm long | 28-31 | 38-42 |
Torque Settings according to Clymer's:
Chapter 10, table 1 it gives specs only as torque and the text says to do it with a criss cross pattern. Doesn't mention the adapter. Values shown are:
BMW Models 1970-1988 | lb-ft | Nm |
1970-1978 | 16-17 | 22-24 |
1979-on (Except R100GS) | 23-30 | 32-42 |
R100GS | 26-33 | 35-45 |
BMW tool 00.2.560 - adapter for torque wrench to torque bolts holding drive shaft to transmission output flange Specifications:
Center to center is 44 mm . It's just a 10mm 12 point box wrench cut off and jammed into a 3/8 " drive adapter. Note that the torque wrench fits in from the BOTTOM of the wrench in the right hand photo.
Click on the pics to get BIGGER view.
BMW Tool 00.2.560. 

A homemade adapter - note the over-all length of this
one is 5 inches (125mm) and center to center of wrench end to socket is
4 inches (100mm).
To use this you must calculate the leverages and work
out the correct torque figure. Best bet would be to duplicate the dimensions
of the genuine BMW tool, then you can use the factory specs.
BMW
R100GS ignition switch removal - a tricky one - but not bad if you know how!
Info by Philippe Gouraud, UK, (Philippe[Hannibal] on the HUBB)
Philippe says:
First, Remove the small plastic outer ring:
It removes with three small (and fragile) plastic outer clips. Lift the ring with a small metal blade - or strong fingernail.
Next, see picture below:
Finally, disconnect the plug under the tank.