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I own a 1977 R100SRS - its a rare R100RS with an S fairing in Motorsports colours. It was originally intended as an Australian police bike but was a cancelled ordered.

The problem I have is the starter motor won't turn.When I lifted the tank a relay was burnt out - but the relay isn't on the standard R100RS wiring diagram.

From left to right looking at the relays (on the left hand side under the tank):
The first is a horn relay - it's pinky purple in colour and plugs into a mount. I have confirmed its the horn replay because when I pull it out the horn doesn't work!
The second is metal. I presume its the starter relay. It also plugs into a mount.
The third is mounted by a screw on the frame next to the starter replay. There are four wires that go into it (#13 green with a purple stripe, #5 red, #10 brown and #8 green with a black stripe). The red is +, the brown is – and they are on constant. The green wires: one is negative and the other comes on when the ignition is turned on. The numbers mentioned above are stamped on the wire connectors protective sleeves.

Could this be a load shedding circuit? Anybody know what relay number it might be?

I posted this on another forum without success.

R100SRS wrote:I own a 1977 R100SRS - its a rare R100RS with an S fairing in Motorsports colours. It was originally intended as an Australian police bike but was a cancelled ordered.

The problem I have is the starter motor won't turn.When I lifted the tank a relay was burnt out - but the relay isn't on the standard R100RS wiring diagram.

From left to right looking at the relays (on the left hand side under the tank):
The first is a horn relay - it's pinky purple in colour and plugs into a mount. I have confirmed its the horn replay because when I pull it out the horn doesn't work!
The second is metal. I presume its the starter relay. It also plugs into a mount.
The third is mounted by a screw on the frame next to the starter replay. There are four wires that go into it (#13 green with a purple stripe, #5 red, #10 brown and #8 green with a black stripe). The red is +, the brown is – and they are on constant. The green wires: one is negative and the other comes on when the ignition is turned on. The numbers mentioned above are stamped on the wire connectors protective sleeves.

Could this be a load shedding circuit? Anybody know what relay number it might be?

I posted this on another forum without success.

Welcome to the forum. I hope you have better success here.

It appears that you have identified the starter relay correctly. And the starter relay or the socket it plugs into would be my main suspect. There is a particular problem that seems to come with the under the tank master cylinder bikes. And unless yours has been updated with a handlebar mounted master cylinder that would be my main suspect.

The problem is that brake fluid from a leaky under tank master cylinder has a tendency to wick into the starter relay socket. That socket and the relay is the only path from the positive side of the battery (via the starter solenoid) thence to the headlight shell ignition switch. But that wouldn't appear to be your problem. However that same starter relay or socket could easily be the culprit on your starting problem. You will need a good relay of course. I would buy a new starter relay. If it wasn't the relay, then you have a spare known good relay, which you are likely to need some day.

The other thing that needs to be done is to clean the contacts in the socket for the starter relay. This gets gunked up from the wicking brake fluid. Cleaning is easier said than done, since the contacts are recessed. A toothbrush and some good contact cleaner, along with elbow grease will eventually get the job done.

There is another thing you might want to check if the starter relay and socket seem OK. There is a black wire between the starter relay socket which goes into the top engine cover. That wire activates the starter solenoid, which in turn thrusts the starter gear into the flywheel while supplying high current to the starter motor. To check out that you would need to have a jumper wire from the positive pole of the battery and touch it to the black wire to the sonenoid. Probably the easiest place to do this would be to find the appropriate terminal on the starter relay socket and do the touching there. When you do that the starter will immediately energize, and if the ignition switch is on the motor will start.

As far as a "load shedding" circuit, I'm not sure what that would be but I am sure that your bike doesn't have it.

Do you have good wiring diagrams to work with? It helps to know what is going on inside the starter relay and to know what color wire goes where on the starter relay socket. And for that matter, you can figure out the whole starting circuit if it comes to that.

Good luck.


Ken

Ken -

Yeah, we were not able to help him out on another vintage forum. The thing that strikes me about this is the terminal numbers the OP provides. Where are those on this bike? BMW used DIN standards and I can't find any relays or devices in the wiring diagrams with those terminals. I suppose one could try and match the wire colors, but that is even harder.

Getting a picture of this device sure would help IMO.

Kurt in S.A.

http://www.carandclassic.co.uk/car/C373701

If indeed this was a police order, then could this relay have something to do with what coppers had for extra equipment?

Would a diagram from a '77 R100S do the job? Which might be closest...the S or RS wiring diagrams? Did the wiring change much on the S and RS bikes from 77-80?

What does a vin search describe it as? http://www.bmw-z1.com/VIN/VINdecode-e.cgi

A quick google search has the R100SRS as either a 78 or 79 model mostly.
http://books.google.com.au/books?id=dGY ... RS&f=false

I have heard that the Motosports were,

Australian police orders
Belgium police orders
Swedish police orders

Had blueprinted engines/did not have blueprinted engines

Take your pick of all the stories, I have a feeling that the truth is a bit more prosaic, they were just another Bmw special paint job.

Apparently they have some Ozzie compliance info on the id plate. It might add to the suspicion of their history.

From the link above...

a cancelled order for the Australian Police force and authenticated by the plate confirming type approval by the Australian authorities on the top surface of the swinging arm and the frame and engine numbers.

Yep they have an Australian compliance plate fixed to the top of the swinging arm. They are real. I have two of them

Anyway, After a day spent with a Power Probe I (great tool) the answer is…drum roll…

The second replay, which is the starter replay, was broken. Got an $11 one from the local Auto shop and it kicked straight away. Moral of story – check the obvious things first and don’t fall for the non-related problem (melted third replay). And of course, because I had the relay removed the power was cut to all circuits (87+87a)!

Now…for the third replay – a bit more complex.

It looks like the third replay is an indicator and hazard circuit energising replay.

After some detective work – I believe that this is the way it is supposed to work: The green and black wire goes positive on ignition on. This couples with the brown wire (earth) to trigger the replay. The red (positive) and green and purple then energise the indicator and hazard circuit energising replay. This means that the indicator and hazard circuit only works when the ignition is on.

Looking at the hazard switch wires – a wire has been jumped, which might have been a factory adjustment. I have attached a couple of photos on this switch.

Recall that this bike was one of 25 built for the Australian Police force so the hazard circuit might have had additional power items – hence the relay.

Does the power on only hazard switch sound normal?

Does the wiring going to the hazard switch look normal?


Not sure if these links will work here:
http://i749.photobucket.com/albums/xx13 ... 310088.jpg

http://i749.photobucket.com/albums/xx13 ... 310089.jpg

Right click both images..

Hi, did you ever find wiring diagrams that work with this BMW? It sounds like my bmwr100rs and it is not wired as the Haynes or Clymer diagrams so after a couple of years off the road I am now struggling to get the electrics to work. Cheers Mark

Wow!
This topic is from a decade ago!

Maybe you should remove the starter cover and see if your starter works when jumped (hot-wired).
Then work your way back from there.