The Airheads Beemer Club is a non-profit club reclaiming the 'Legendary Motorcycles of Germany'

Topic-icon ‘76 R90S. Electrical issues.

  • mikethebike
  • mikethebike's Avatar Topic Author
  • Offline
  • R100 Level
  • R100 Level
More
3 months 1 week ago #5943 by mikethebike
‘76 R90S. Electrical issues. was created by mikethebike
Before I jump into this problem which I fear may be large. I thought I’d just check to make sure there isn’t something very obvious that I am overlooking.
This bike sat for many years in relative shelter. In an open ended building, but in a quite dry climate. In the far right of Washington State.
The issues:
I installed a fully charged XL30 AGM, new +&- ve cables to ground and starter.
Here’s what works, parking lights, same lights with ignition on.
Headlight flasher works as does the headlight.
Signal lights both sides and dash.
Break light on both brakes.
Light switch appears to work but no high and low beam.
Engine off/on/off switch appears to work as I get dash and tail lights.
Power to the coils and I get a nice bright spark when opening and closing the points.
What’s not working:
Starter does not engage when button pushed.
Horn .

I’ve just repaired the brake master cylinder as it lost all its fluid, I don’t know how long this had been an issue, but it was long enough to attack the paint of the main top tube of the frame.

There was evidence that the previous battery ( probably the original) had at one time puked out enough acid to put various frame parts around the right hand side swing arm pivot.
I have installed an electronic charge relay thinking it was problematic.

Both fuses on the connector block are in good shape, zero resistance across them.

This is either something very simple or I’m going to spend a long time tracing power
Thanks in advance
Michael

Please Log in to join the conversation.

More
3 months 1 week ago #5944 by 8166
Replied by 8166 on topic ‘76 R90S. Electrical issues.
I'm not very familiar with the wiring on an R90S, but it sounds like you soon will be. ;)

Start by locating a schematic for the bike, and identify the elements involved in the starting circuit. Begin with the starter button on the handlebar, I'm guessing one side goes to the battery, and the other side goes to a starter relay. The starter relay may be located under the fuel tank, and it could be it's close enough to that leaky master cylinder to have also been crapped up, too. Take the relay out of its socket and examine it for any external damage. If it looks good, clean the terminals on it, then clean the terminals in the relay socket. You can use a pen knife or some sandpaper, but I found a set of diamond files on the Proto tool truck that are sized especially for cleaning terminals. Finish up with a spritz of compressed air, then a squirt of DeOxIt to keep the terminals clean. Then try to start the bike again.

If that doesn't make any difference, look at the schematic and trace the voltage from the battery, through the handlebar starter switch, to the starter relay, on to the solenoid on the starter, and then to ground, making sure you've got voltage or ground at each place when appropriate.

You could also try listening for a click at the starter relay when you push the starter button.

Try this, and let us know what you find out.

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.

Please Log in to join the conversation.

  • mikethebike
  • mikethebike's Avatar Topic Author
  • Offline
  • R100 Level
  • R100 Level
More
3 months 1 week ago #5946 by mikethebike
Replied by mikethebike on topic ‘76 R90S. Electrical issues.
Thanks Scott
I’ve got a good clear schematic ( 2 actually, one in workshop manual and a great coloured one from the Airheads library.
I’ll stay with the starter relay, it us directly under the Master cylinder.
Then move on to the actual handlebar switches, they’ll need a clean after all this time anyway.
That’s tomorrow’s tasks.
M

Please Log in to join the conversation.

More
3 months 1 week ago #5949 by Wobbly
Replied by Wobbly on topic ‘76 R90S. Electrical issues.

mikethebike wrote: What’s not working: Starter does not engage when button pushed. Horn.

I’ve just repaired the brake master cylinder as it lost all its fluid, I don’t know how long this had been an issue, but it was long enough to attack the paint of the main top tube of the frame.

The Starter Relay physically sits just below the Brake M/C. Anytime brake fluid leaks from the reservoir on the under-tank m/c Airhead models, the relay takes a bath in a caustic liquid that is harmful to the relay connections AND the contacts inside the relay. A very serious look at the relay connections and functions is probably in order.

Don't hide 'em, Ride 'em !!
#15150

Please Log in to join the conversation.

More
3 months 1 week ago - 3 months 1 week ago #5952 by bremoit
Replied by bremoit on topic ‘76 R90S. Electrical issues.
Boxer 2 Valve has a video on their YouTube channel covering test procedure on the starter relay for the /6 series. Checking the relay would be good place to start, as noted above.

www.boxer2valve.com/

www.youtube.com/results?search_query=boxer+2+valve
Last edit: 3 months 1 week ago by Wobbly. Reason: Mods added links

Please Log in to join the conversation.

  • mikethebike
  • mikethebike's Avatar Topic Author
  • Offline
  • R100 Level
  • R100 Level
More
3 months 1 week ago #5957 by mikethebike
Replied by mikethebike on topic ‘76 R90S. Electrical issues.
Wow,
I’ve never seen Boxer 2 Valve before. I’ve been playing on airheads for about 15 yrs and never knew it existed fir either parts or the videos. Thanks for the info. Now I have something else to binge watch for the next few weeksLOL.
Michael

Please Log in to join the conversation.

Moderators: 8166Wobbly
Time to create page: 1.058 seconds