GT550 Electrical Issue

[74GT550]

My 74 GT 550 is running great but has a random electrical issue. One time after stopping for 10min, I turned the key on and no power. Nothing. After sitting for another 10min I turned the key and the lights came on and I started it and ride home fine. Yesterday I came to a stop at a light and it just died, no power. Cycling the key did nothing. I tapped the side cover where all the relays are and the lights came back on, fired it up and I rode home. Any thoughts on what to check?

Thanks

[PHPaul]

Sounds like a loose or corroded connection to me. There are no "relays" in the stock configuration. The closest thing to a relay is the starter solenoid and maybe the turn signal flasher if you stretch the definition, neither of which affect power to the wiring harness.

There are several "bullet" type connectors in the wiring harness between the battery and the switches on the handlebars, including a couple on the ignition switch itself. Any of those could be loose, corroded or the wires frayed.

Another major suspect, particularly as tapping on the left side cover seems to affect the problem, is the "fuse holder". It's a poor design to start with, 40+ years haven't improved things any. It's basically two half clips that snap over the ends of a glass cartridge-type (AG) fuse. If they're loose and/or corroded, that would sure account for the problem.

When I rebuilt the wiring harness on my '74 I eliminated that fustercluck and went with a modern ATC blade fuse and holder.

[yeadon_m]

Classic one might be a cracked or lose / corroded battery post for positive lead?
Mike

[jabcb]

In addition to what was suggested…

Replace the fuse even if it looks good. I had one go bad that still looked good.

Check the multi-wire connectors for a wire that has backed out of the connector.

Make sure the battery has a good charge.
Will the key switched on & the kill switch set to off (to protect the coils), pull on the wires & connectors at various locations to see if you can make the lights go out.
Recharge the battery after you are done.

If you can’t find the location, use a multimeter to check for voltages.
There is a good chance the problem area will have a larger-than-expected voltage drop.

[74GT550]

Thanks for all the info. Pretty sure i've found the culprit. The bullet connectors at the fuse holder are completely shot. Looks like the rot is into the wires so I'll trim them back and mount a new style fuse holder, this would also explain the slow starter motor. Should have it going by the weekend to make some smoke.

Cheers



Here's a pic of the bike:

[PHPaul]

Ayuh, I'd say you found it.

The rest of the bike looks cherry!

[74GT550]

Thanks PHPaul - Turns out the positive battery cable was also completely rotten. I replaced it and added a modern fuse holder and went riding.

[2strokelove]

Check this site out. I invested in this long ago. Great quality connections that look stock.

http://vintageconnections.com/" onclick="window.open(this.href);return false;

[PHPaul]

+1 on Vintage Connections. I'm on my fourth order from them: 2 kits (bullet connector kit and non-latching multi-pin connector kit) plus 2 refills for the most-used parts (male/female bullets, 2 & 3 pin connectors).

Excellent product, dead nuts perfect replicas of what's on my '74 GT550, decent prices, fast shipping, excellent service.