Topic: electrical issues 1972 cb500

[Yert315]

Bought a 1972 cb500 a month back and have been slowly getting her fixed. Every once in a while the bike would lose all power when riding. It would start back up eventually. On my way home about a week ago the bike completely quit.  When I say no power, I mean no dummy lights.

Here's what I've done:
- fully charged the battery
- checked the fuse (only one on this bike) and it's good. swapped another just in case. no dice.
- tried jumping the ignition switch. black and red wires? still nothing.
- tried wiggling any wire loom I saw to see if it would help. nothing.

The headlight bucket is off the bike, so the wires are just hanging there. I went through the wiring diagrams and did the best I could tracing any main power wires.

What is my next plan of attack here?

Thanks,
Trey

[vonvendetta]

A few things can cause this so I will try to help but be warned, I am a complete noob.

1. This sounds like a wiring issue 99.99% Trace the wire that goes from the battery to the ignition switch, which is the one the fuse is connected to. Make sure it is a solid connection all the way into the key switch.
2. I would check the ground coming off the battery
3. If that still doesn't work I would consider making a quick troubleshoot wiring harness.


If 1 and two didn't work it is probably because you have 40 year old wiring in need of some new connections.

[bryanj]

You have a bad connection somwhere, use a Multi meter or a bulb with two leads and check for voltage at every connection starting at the battery and working along

E.G
First check ground wire by putting -ve to engine and +ve to battery then

-ve to ground of battery and  +ve to other terminal, move it to other end of red wire, then end of fuse, other end of fuse etc etc

At some point you will get no light or no voltage reading so your fault is between the last good point and the first bad one

[Yert315]

Figured I'd close this thread with a solution. Turns out the square connector for the ignition switch was badly corroded. I cut it out and spliced the wires together with crimp connectors and its working fine now.

[Vinhead1957]

Sounds like the key switch may be acting up!  Turn the key back and forth to see if it is intermittent