R65 Earth ground points

[MatthewH]

My 1984 R65 (UK model) is (still) in the process of having its cafe-racer modifications undone and returned to something close to stock.  When I got it the ground wires or earthing points were all disconnected, and the wiring harness / diagrams give no clues as to the earthing locations, i.e. where they're bolted to the frame etc.

There is obviously a bundle of wires from the loom that attaches to the battery negative terminal; there is what looks like a braided earthing cable that needs to attach from battery negative to somewhere.  Can anyone help and tell me where the earthing points are for the various cables please?  Thanks all.

[nhmaf]

The negative terminal on the cable is traditionally connected to the chassis/engine/gearbox through the special hollow bolt which goes into the rear cover of the gearbox just above the rubber bellows/swingarm boot where the driveshaft is attached to the gearbox output.
The special hollow bolt also has a long narrow "nose" which serves to secure the speedometer cable which goes down into the gearbox cover just above it.   The bolt is hollow so that it can also vent the gearbox and prevent pressure buildup in there.  It is easy to strip the threads in this bolt, so sometimes people use another gearbox cover bolt which is directly next to this special one to handle the battery terminal grounding duty since the special bolt already has other duties it needs to do (single point of failure for several systems).

There should also be a frame attached grounding point up under the fuel tank in the vicinity of the coil where several brown wires (ground) are to be attached.   Do you have a Haynes or Clymer manual?

Somewhere on this site we do have a PDF version of a wiring schematic...

[Barry]

You mention several earth connections to the battery. There would originally have been only one main earth connection to the battery with all the harness earth wires connected to the frame as nhmaf described. There should be 2 connections to the +ve battery terminal, one heavy cable to the starter solenoid and  another smaller cable into the harness.  Anything else is a modification. One reasonably popular and useful mod was to run a separate earth cable to the diode board. If you have that it would be worth keeping.

Take a look here for your wiring diagram

http://bmwmotorcycletech.info/R65Schematic.htm

[montmil]

Matt, Here's where the bundle of earthing / ground wires attach to the chassis:

[Bob_Roller]

Don't know if you would be interested in this earthing / ground wire modification .

I got a large diameter cable from an auto parts store ( about 2.5 times the diameter of the stock cable), removed the stock cable from the transmission bolt .

Installed the replacement cable from the negative post on the battery, to the lower right hand engine to transmission bolt, put it on the nut side, or forward side .

I also made up a large diameter wire with terminal ends on it, ran it from the main grounding point by the voltage regulator, back to the negative post on the battery .

It eliminates the path though the engine, hardware that holds the transmission to the engine, and the path from the main grounding point through the frame, to the engine .

[flybot]

I have one other ground wire not mentioned above, on my '83. There is a single brown wire on the bottom of the engine, near the N switch on the transmission. It is bolted to the case.

[MatthewH]

All super helpful guys, many thanks.  I have the schematic diagram from the Haynes manual but that only tells you which components the wires run from rather than the real-world fastening locations on the bike itself.   Problems solved though, everything should be sufficiently grounded now! - thanks again all.