R75/6 Ignition switch rebuild possible?

[opposedtwo]

Hi All!

First post from a new airhead owner.

Recently picked up a 1976 R75/6 in pretty decent condition. Rebuilt the carbs, and she was running quite well!

Yesterday, I was out for a ride. Parked the bike, met some friends, then went to start it up about 30 min later. Turn the key: no power, no lights, no dash lights, no power period. Turn the key again: power. Okayyy, start and drive 25 feet.. put put die: no power!

I did some roadside checks: battery terminals tight and in good shape. Battery ground tight and in good shape. Next I pull apart the headlight to gain access to the ignition switch and circuitry. Check the connectors on the ignition barrel, everything seems tight and okay. Try switching the 30 Amp red wire on the circuit board to the auxiliary 30 Amp circuit, no result. (The bike is new to me, and I am not very familiar with it as of yet. I assume the extra 30 amp terminals on the circuit board behind the headlight are auxiliary circuits, and you can simply switch between the two?)

Next I disconnect the wires from the ignition barrel, and try to jump the red power wire to the others (just touching the wires together), in turn, to see if I get power. Presto! Red to single green gives me lights, and red to the double green wire gives me signal lights, and power to the ignition.

This means, to me, that all relays and associated things on the circuit are working fine, it is simply a faulty ignition switch. Does my logic check out?

And.. what all of this leads me to asking: is it possible to take apart the ignition barrel and check/repair the internal contacts?

I did not seem obvious that the ignition barrel will come apart.. but I am hoping that it will. Please, experienced ones, bless me with your r75 knowledge

Thanks a lot guys!
Stu

[Bamboo812]

First I'd check if the plate the connectors are attached to is loose. I've heard of people fixing a similar issue by pressing down on it and re-crimping the bent tabs that hold it in place for better contact.

[opposedtwo]

First I'd check if the plate the connectors are attached to is loose. I've heard of people fixing a similar issue by pressing down on it and re-crimping the bent tabs that hold it in place for better contact.

Thanks for the reply. I don't follow however

Which plate are you referring to?

The connection / connectors on the back of the ignition barrel seemed secure and in good shape. Likewise on the main circuit board.

Thanks,
Stu

[Bamboo812]

I'm not talking about the connectors themselves, but the round black plastic piece they are mounted into. It is held in the body of the switch by three crimps around the edge. Try wiggling it around. If it can move at all, the internals may not be making good contact.

[opposedtwo]

I'm not talking about the connectors themselves, but the round black plastic piece they are mounted into. It is held in the body of the switch by three crimps around the edge. Try wiggling it around. If it can move at all, the internals may not be making good contact.

awesome, will take a look. Thank you!

[Ken in Oklahoma]

Hopefully the advice you've received will solve the problem for you. But if you're still scratching your head here's something you might try, since you're suspicious of ignition problems.

Hotwire the ignition. Run a wire from the positive battery post to the positive side of your twin coils. (The coils are wired in series, not parallel). Now thumb the starter button and see if the engine catches and runs. If so you've narrowed your problem down to a more manageable one.

If you don't know, the /6 and /7 airheads with the under-the-tank master cylinder have a chronic problem. What happens is that the master cylinder eventually leaks and brake fluid dribbles down and into places where you don't want it. With the tank off the bike look on the left side of the top frame tube and you will see a relay that is plugged into a socket. That socket has female pins pointed upward and what happens is that those pins get corroded, oxidized, and dirty, with the problem exacerbated by brake fluid dribbling down and onto the pins. What you will need to do is to remove the relay and clean the relay contacts with some contact cleaner. Use a fine wire brush if needs be. You want to see clean copper. Also the pins in the socket are even more likely to be corroded and are hard to get to . You will need to clean those pins with a toothbrush and some contact cleaner. It's not an easy task to do. You may want to judiciously 'scrub' the sockets with a small wire brush, being careful not to have a wire brush whisker break off and lodge into the socket.

On both my '76 R75/6 and my '77 R100/7 I left a neatly installed hot wire in place, only this hot wire has a toggle switch in the middle of it. With the toggle switch off you have the key and ignition switch switch operating as designed. However if you suspect a problem in this area you can then flip the toggle switch and run 12V to the input side of the two coils (the negative side of the coils goes down into the starter cavity to the points).

BMW so designed the electrical system such that the 12V needed at the rear end of the bike and the 12V that are needed at the front of the bike are connected to separate pins in the starter relay socket. The relay itself has an internal connection which joins the front and the rear 12V connections together, thus completing the wiring harness, as it were.

Ken

[opposedtwo]

Hi Ken, thanks for your response. Here is what I got up to last night:

So first I checked the starter relay, oh ya it was full of sh!t



I got the terminals on the relay cleaned up pretty well with the assistance of contact cleaner, wire brush, and some 1000 sand paper. I just squirted some contact cleaner through the female connectors.

Next checked the ignition switch for continuity, was reading 0.6 Ohms (which i guess is fine??) with the switch engaged, as you would expect. The poles on the ignition barrel seem pretty loose and wiggly. I was not sure how to pull it apart however, and even further not sure what I would find once I got it apart, so I left it be.

Hooked everything back up on the bike, and presto I have power again!

I'm not convinced I have everything connected correctly however. On the ignition barrel I'm only using the terminals: 15 (double green wire), 30(double red wire) and 58 (grey wire).

Everything works correctly with this setup, with the exception of: when the key is turned to the first (park) position, and the lights are set the the first (park position) I get power to the starter button. However if the lights are in the off, or full on position I get no power to the starter button. All of this with the key in the first "park" position. It seems odd. Can anybody else confirm for me that this is the case with their bike?

I'll get some more pics tonight. There seems to be a green wire, and a black wire floating around in the headlight which I am not sure where (or if) they should be connected to. In my hasty roadside dismantling I made the rookie mistake of thinking I'll remember how to hook everything up the same

[Texer]

Not really a help, but I purchased '74 60/6 this summer and had some no-power issues at the store, gas station etc. when I'd try to start. No dash lights, etc. After fussing with looking into the bucket and checking the wires, always a start after all. Like voodoo. Happened like 4 times and on a Sunday I just started at the ground post and began cleaning house by addressing a all connections for dirt and fit and dielectric grease till I got back to the positive post. On the way I found a short jumper wire to the fuse was intermittent when moved around. I danced for joy. Then I made a new jumper. No issues since.

[opposedtwo]

I went through everything again last night to double check. Everything appears to be peachy except the park position power to starter button issue (or non issue?).

So, I jumped the red hot wire to grey park circuit wire to double check that the ignition switch is not connecting circuits that it should not: (blue wire is my jumper).



Again, with the park circuit powered, lights switch in park position, and kill switch set to run, I am getting power to everything with the exception of headlight Hi/Lo beam. I get dash lights, and power to starter button etc.. Is this normal?

If I turn the headlight switch to either off or on position, (or kill switch to stop) this cuts power to everything with the exception of parking lights, and speedo/tach backlight.

These results are exactly the same as when I have the ignition switch hooked up, and the key in park position. ie this is not a fault of the ignition switch. It is either a) not a fault at all or b) something is hooked up incorrectly or shorting.

Next I took the left handlebar (light) switch apart and took a look, at bit dirty but no burned looking wires. Sprayed some contact cleaner in there and put it back together.

This is how I have my ignition switch hooked up:



Green to 15, Red to 30, Grey to 58. I've seen in wiring diagrams that there should be another green wire going to 56, and I have a spare green wire floating around in my headlight bucket, but I do not see where it should be attached to?

spare green wire:



both green posts on the right side of the board are in use. However on the left side of the board only 1 terminal:



So. If my power on park cicuit is a fault (could somebody please check on their bike, Im assuming you ride it ) it's probably as you say Texer, check for short circuits and bad grounds.

cheers guys

[opposedtwo]

So, I've figured it out.

It turns out that the answer was staring me in the face the entire time, and well, I should have realised it sooner. Anywho, that lesson that I have slowly been learning that states don't take things apart without first taking pictures of it or knowing how to put it back together has once again been impressed on me.

I remember having a green wire, and an empty green terminal on the circuit board, so therefore the green wire was attached to the empty green terminal on the circuit board.

Now, I have been looking at the wiring diagram tracing wires, and thinking well "I don't have a green wire going from my left handlebar light switch to my ignition", and therefore mistrusting the wiring diagram.

Yes, I am sure you can all guess my conclusion: the empty green terminal is to remain empty, and that wire coming from the left handle bar should be attached to the ignition switch, as it was originally.

I'll add some pics for reference. Hopefully it helps somebody in the future.





Leave the top terminal empty, connect said wire to post 56 on the ignition.

All said and done. Everything is now working A OKAY and I changed the fork oil, and adjusted the valves last night as well. Now to ride it :ricky

Thank for your guys assistance, and certainly to anybody who reads this, clean your starter relay!

I'm not sure what the original fault was, but the starter relay is sure dirty. My ignition switch is not in top shape, and I'll carry an toggle switch which I can quickly pop on to power the ignition in case it dies while on the road).