"R" Bike Starting Problems?
Click, Click, Click, . . . Is that all you hear sometimes when you press that starter button? Chances are, that the clicking is coming from your bikes starter relay (located under the fuel tank in /7 models). If so, it is telling you that you better replace it before you are forced to walk home soon. Usually, this "clicking" instead of actual starter operation begins intermittently and gets progressively worse over a short period of time. That's lucky and allows you time to procure a new one before it's time to walk.
When the starter relay began failing on my '78 R100S, I did a quick repair since there is no dealer in my area. I simply removed the relay cover (it was not designed to be removed), cleaned and filed the contact points. It worked fine and gave me additional time to get up an order big enough for a dealer to ship me without the freight costs exceeding the parts costs. This fix though, must be considered a short term fix. Relays and switches are usually made with a hard coating on the contacts to resist wear and pitting due to arcing of the electrical current when operated. When this coating is burnt through, the relay or switch is no longer reliable and must be replaced. Filing and cleaning the contacts only removes the built up oxidation but does not replace the coating. Very rapid deterioration will continue.
I did some checking before purchasing a new relay. The OEM relay is made in Germany by Bosch (or for Bosch by somebody else), and is rated at 30 amps. It also costs too much. I found an "almost" equivalent relay at Radio Shack (part number 275-226) for around $6.00, about one third the cost of an OEM unit. It is made in Holland, and is also rated at 30 amps. The appearance is almost the same, the size is the same, and the electrical pins are in the same arrangement, the same size, and are numbered the same. There is a plastic mounting tab on the Radio Shack relay that you should cut off to get it out of the way since it is not needed. The coil circuit is controlled by the pins numbered 85 and 86. The high current contacts are connected to pins 30 and 87. The only important difference is that one pin is missing (see the figure below), the OEM relay has two number 87 pins where the Radio Shack relay only has one. In the OEM relay, those two number 87 pins are connected to one another internally so that the two wires connected to them are always connected to one another. In order to use the Radio Shack relay, therefore, the two wires that plug into the relay pins numbered 87 need to be connected to each other by another way. An easy way is to solder a jumper wire between these two wires right where they enter the connector block at the relay.
To do this, remove the two large diameter red wires from the connector block by depressing the locking tab on the connector and withdrawing the wire. After soldering the jumper wire in place, make sure the locking tab is protruding from the connector end on the wire and simply insert into the connector housing until the connector snaps into place. The amount of current carried by this jumper wire is sufficient enough to require a large wire for this purpose. Use a number 12 or larger wire gauge and do a specially good job since this jumper carries the electricity that operates everything on your motorcycle except the starter.
Now simply insert the new relay into the connector right where the old relay was removed. In the event of a future relay failure, a replacement can be had from one of the thousands of Radio Shack outlets rather than a "not always convenient" BMW dealer. If you choose to use an OEM relay in the future, no change is required. Just insert it into the connector. The jumper you installed will be redundant to the connection in the relay and affect nothing.
The solution outlined above works in models that use the BMW part number 61- 31- 1- 243- 207, all /7 models. You may find that a similar solution may work for other models. I also use the same relay for my headlight relay (with a few minor changes as well) so I carry a spare in my toolbox and can use it in either location if needed while traveling.