No Electrical Power

I need some expertise/experience.

1974 R90/6. Been running super all summmer.

This morning after riding about 40 miles, when I pulled in the clutch as I was stopping for a red light, with the right turn signal on, the engine stopped, and I had no headlight, no instrument lights, no starter, nothing.

Put the bike in neutral, turned off the ignition switch, and pushed it off the road where I could look things over. Symptom was exactly as though the battery ground cable was loose. No electrical power at all.

Checked both ends of the ground cable (trans and battery), nothing loose. Spent about three minutes thinking about it, turned the ignition switch back on, and bingo!, oil, neutral, and charge lights lit. Pressed the starter, it fired right up, and I drove the 10 or so miles home. During the trip home, I stopped at several stop lights, used the turn signals, no problems.

Parked the bike in the garage and after a cup of coffee, I turned on the ignition switch (without starting the motor) and again, oil, neutral, and charge lights lit like normal. I pulled in the clutch, no change. Stepped on rear brake, no change. Pulled in front brake, no change. But, when I turned on the right turn signal -- lights out. Same symptom as before, as though I had no electrical power.

I checked battery, good voltage. I check battery connections, nice and tight. Checked ground on tranmission again, good.

Thought it might be the ignition switch (it is the original switch). Disconnected the red wire at the at the ignition switch (the one coming from the starter relay), approx 12 volts on the red wire. So, switch is getting power.

Disconnected the green wire from the back of the ignition switch (green wire goes from the igination switch to the terminal block inside the headlight shell). When the ignition switch is turned on, I have 12v between the spade on the back of the switch (where the green wire attaches) and ground.

So, not the iginition switch?

I pulled both of the 8A fuses, checked them (good), and cleaned up the ends.

No change in symptoms.

As info, overall, the electrical system is in ok shape. Over the years, I've cleaned up connectors, I've got star washers on the frame grounds, so I'm puzzled.

What component would fail, or which wire would break, that would cause the symptoms I described?

As additional info, because common wisdom is to always look at what you did last - I had the right turn handlebar assembly off about two weeks ago while I installed the tri-angle wedge that had been missing for 20 years. I've probaby ridden the bike eight times and several hundred miles since then.

So, I unfastened the right switch (removed the two small and one large screw) and can't see any broken connectors or piched wires. I also checked the handlebar mounted brake light switch and both wires and their connections look ok.

Not sure how a problem with the right handlebar wiring could cause the described symptoms, but that was the last place I was working on the bike.

And the one common thing is that the turn signal was on both times when I lost power.

The turn signal relay is the original. It looks ok inside, no visibily damaged components or sticking contacts. If it has failed, would it cause the symptoms I am experiencing; or, just loss of turn signals?

Any ideas?

Any recommendations where to check next?

Regards,

Barron

I wonder if the turn signal is a red herring. How about cleaning the contacts on the starter relay under the tank? Left side of the backbone about mid way back. Pull it out, clean the male contacts, then plug and unplug it a few times. Snowbum even has a mod which externally connects the two red wires that go in and out of the relay as a way of bypassing this situation.

I am no electrician... but it sounds like a diode board ground going bad... I would check that. Also, it does sound like a relay problem... and I know from experience that they can look okay, but are internally be broken. I would check the relays individually, clean all the connections real well, you should find the loose ground.

Well, the diode board is part of the charging system..and that seems to be working fine with no red light and plenty of power when the key is turned on.

This has something to do with actually running the engine..which is battery, coils, switches, ignition, and spark plugs.

Any chance you slightly pulled the wires for the right switch assembly and loosened the connections in the headlight?

Did you notice if the handle bars were turned both times as well as the right signal switch?

You could have a short in the turn switch wire harness grounding the live wire to the starter/engine and killing power to the coils.

Start the motor on the centerstand and individually - turn on both signal lights, same with turning the handle bars, same with gently pulling on the wire harness.

See if you can recreate the failure point when you're not riding.