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Hi, I'm new to the forum.
I went through the posts but had no luck with my problem.

1974 R90S symptoms:
Instrument illumination lights not working.
Neutral light OUT at idle, ON when engine revved.
Generator light OUT at idle, glows faintly when revved. (voltmeter shows charging is normal when revved).
Turn signals work fine, but indicator light is intermittent.
Tail light (running light) not working.
All other electrics working fine.

I have verified all bulbs.
I have taken the instrument cluster apart and verified the circuits in the plastic 'circuit board'. They are suspect but I beleive the contacts are all good.
Harness plug looks O,K. but I don' t know how to properly test it.
I have tightened all ground connections I could find.
I am all out of ideas with my limited knowledge of electrics, so any help is welcome.

P.S. Can I change the kickstarter seal without removing the tranny and/or cover?

JoeBullet wrote:Hi, I'm new to the forum.
I went through the posts but had no luck with my problem.

1974 R90S symptoms:
Instrument illumination lights not working.
Neutral light OUT at idle, ON when engine revved.
Generator light OUT at idle, glows faintly when revved. (voltmeter shows charging is normal when revved).
Turn signals work fine, but indicator light is intermittent.
Tail light (running light) not working.
All other electrics working fine.

I have verified all bulbs.
I have taken the instrument cluster apart and verified the circuits in the plastic 'circuit board'. They are suspect but I beleive the contacts are all good.
Harness plug looks O,K. but I don' t know how to properly test it.
I have tightened all ground connections I could find.
I am all out of ideas with my limited knowledge of electrics, so any help is welcome.

P.S. Can I change the kickstarter seal without removing the tranny and/or cover?

Hi Joebullet, welcome to the forum.

Electrical problems can be about the most vexing kind of problem on these old bikes. Reading through your symptoms nothing came immediately to mind. Perhaps I and others can be of a little more help to you if we get some information.

I would like to get a bit more background information on your bike so I can form a better mental picture of what might be going on. For example, is the bike new to you or do you have a significant amount of experience with it?

Going on with the questions, did the problem suddenly happen, and if so under what circumstances? Do the problems you noted all happen at the same time all of the time, or are they intermittent or inconsistent?

Do you have a wiring diagram for your bike, preferably a colored one such as in the very large Clymer book on airheads? If a person is going to troubleshoot electrical systems a wiring diagram is a must. Wiring diagrams are available on the internet, but I don't have any links for you to click. Google R90S Wiring Diagram and you'll likely come up with what you need.

What are your electrical capabilities? Our answers to you are going to be framed differently depending on whether you're a seasoned electrical trouble shooter or a newbie who has never looked at a wiring diagram, or something in between.

I think you get the drift.

Now for something that might actually be useful. Intermittent or goofy acting electrical functions are often due to bad connections. On a bike as old as yours is (and mine are) they have had plenty of time to develop corroded or dirty connections. On a /7 bike (with which I've had my most electrical experience) one particularly troublesome area is where the starter connector is plugged into it's socket. That would be under the tank on the left hand side, below the master cylinder. What happens is that connection can and does get contaminated (often by fluid from a leaky master cylinder). The gunk and grime screws up the electrical connections between the pins on the starter relay and the mating female pins in the socket. Worse yet, BMW runs the battery power through a couple of those pins, then into the headlight, where the power is distributed by the ignition switch. Even if your problem isn't there, you probably want to spend the time cleaning the pins and socket. The latter is difficult to clean, but it needs to be done.

Also the battery cable ends may need cleaning. Three of them are easy to get at, but the fourth, the positive cable from the battery, is connected under the engine top cover. Luckily that connection seems to give fewer problems than the other three cable connections.

Shifting the subject slightly, the PC board in the instrument cluster may look OK, but it can still have some bad connections. My '76 R75/6 drove me crazy until I discovered about three bad connections where the rows of pins coming in were connected to the flexible printed circuit. I fixed them by scraping some of the protective coating from the flexible printed circuit and then soldering some thin wires to both the printed circuit and pin itself.

Buying a new flexible printed circuit would make a lot more sense than what I did though.

More people will likely be chiming in soon.


Ken

IN GENERAL: weird electrical symptoms are most often related to ground problems, so that's the first thing I'd do: make sure the grounding in the instrument pod is all solid.

My '74 R90S electrical gremlins were evicted using Airbear's most excellent wiring diagrams (and the power of prayer and wearing only my lucky underpants when I worked on the bike).

If you want (and I'm sure Airbear won't mind) I can email both the main loom diagram and the instrument pod diagram. These are for the early '74 bikes only (the ones with the /5 type switches).

DanielMc wrote:My '74 R90S electrical gremlins were evicted using Airbear's most excellent wiring diagrams ...

Indeed, Airbear's diagrams are wonderful. I can particularly appreciate them because a handful of months prior to seeing them I had worked out my own instrument pod diagram trying to ease the pain of sorting out some missing instrument lights (again) on my R75/6.


Ken

Does the bike have the handlebar brake master cylinder?

If so the earth path for some of the instrument lights is earthed via one of the redundant leads to the fluid level warning light fitted to the old master cylinder.

Guess why I know that?

Since Charlie is probably fast asleep in ozland at this hour I'm taking the liberty of posting his diagrams...which, by the way, saved my ass many times on the R90/6....and which I now have blown up, printed and hanging on the garage wall...so for Charlie...



And the other one....


Joe Bullet, hopes this helps for now. I'm sure Airbear will be along shortly, once siesta time is over, and send them to you. Or DanielMc can send them to you..

Sleep well Airbear!

Dunno what happened to my post from yesterday...
Check the fuse contacts. They get corroded and become intermittent. Also check that the fingers that hold the fuses in place are snug against the fuse ends. Another cause of weird electrical action.

You'd probably do well to unplug and replug ALL the possible connections in these circuits. It is possible you have other corrosion causing trouble. Maybe some of the connectors are loose!
Check the inner parts on the tail light socket...read the post a week ago about the bulb that wouldn't light on the bike.

Thanks to everybody for their suggestions.
I now have multiple copies of Airbear's excellent wiring diagrams.
He must be the Guru of the mumbo-jumbo voodoo chile gris-gris black magic spirit of the electrons that seems to inhabit my beemer.
I plan to try all of the ideas, and if nothing works I'll re-post

P.S. Does anybody know if I can change the kickstarter seal without removing the tranny and/or cover?

JoeBullet wrote:Thanks to everybody for their suggestions.
I now have multiple copies of Airbear's excellent wiring diagrams.
He must be the Guru of the mumbo-jumbo voodoo chile gris-gris black magic spirit of the electrons that seems to inhabit my beemer.
I plan to try all of the ideas, and if nothing works I'll re-post

P.S. Does anybody know if I can change the kickstarter seal without removing the tranny and/or cover?

Ah now, don't go assuming that I know much about electrons. I am an Autocad abuser, and the diagrams were my attempt to get to understand a bit of the magic. The symptoms your bike is exhibiting have me completely stumped. Have you tried killing a chicken and checking the entrails for signs?

re your question about the kick-starter seal, I know you can do that with the gear lever seal, so would assume you can. You would need to protect the seal from the shaft splines, maybe with a bit of coke can or tape. Maybe somebody else will chime in and confirm.