[Nordheim]

Hi all, I am the new owner of a 71 CB100 that I am in the process of fixing up. I have always loved this bike from afar and am so excited to now own one as my first motorcycle. I am in the process of fixing this and that, but just encountered a new issue that has stumped me... So, I just installed a new battery and did the trick where I install the battery tender plug to the battery for quick charging, etc. The battery works great, perfect charge of 5.99v and powered all of the lights perfectly. I did mistakenly turn it on with it still plugged in, but everything came on and worked for a long while. Even unplugged it and then continued testing to the same result. I did notice that the left blinker bulb took a while to come on and that none of the side lights were blinking properly: just solidly on. Then, all of a sudden, a little life! Very slow blinking... Then... kaput. All lights shut off. Check the battery, still great voltage. Check cb fuse, fine. Check tender plug fuse, fine. Wiggle switches, nothing. Looking at schematic, it’s hard for me to diagnose what would have caused it. Nothing made a pop or nothing got hot or made a sound. Just everything died. So... any ideas of what happened? I have a few new parts on the way but if any of you whizes know what’s up, I’ll put in an order for whatever you think is wrong. Looking forward to hearing what you think is up! Thanks!

 

[ancientdad]

How's the ignition switch? Bikes that sit for long periods can suffer corrosion on the contacts inside the ignition switch causing a total loss of power after the key is on for a bit, especially when a load is introduced. The old switches can actually be taken apart and cleaned, you'll see "tabs" on the metal circumference of the switch body that bend into openings in the bakelite-style (hard plastic-like substance) backing of the switch where the contacts are that hold it together.

 

[jacksvintage]

How about the flasher unit?

 

[Nordheim]

How about the flasher unit?

Do you mean the Relay? I thought of that too but haven’t been able to test it. My only thought of it not being that is that the tail and headlights are both dead now too.

 

[Nordheim]

How's the ignition switch? Bikes that sit for long periods can suffer corrosion on the contacts inside the ignition switch causing a total loss of power after the key is on for a bit, especially when a load is introduced. The old switches can actually be taken apart and cleaned, you'll see "tabs" on the metal circumference of the switch body that bend into openings in the bakelite-style (hard plastic-like substance) backing of the switch where the contacts are that hold it together.

Ahh, this sounds like a good direction. Will investigate this soon. Did you have this happen by any chance? My bike had been sitting for a number of years w/o power so sounds like it may be the culprit. Probably worth cleaning anyway! if anyone else has any other potential leads, please feel free to share. Thanks!

 

[ancientdad]

Ahh, this sounds like a good direction. Will investigate this soon. Did you have this happen by any chance? My bike had been sitting for a number of years w/o power so sounds like it may be the culprit. Probably worth cleaning anyway! if anyone else has any other potential leads, please feel free to share. Thanks!

Actually, I did have this happen when I was a teenager. My Dad and I were working on used bikes for me as I went from a Honda 50 to a 90 and another 90 and along the way, we encountered an ignition switch or two that either had wires corroded off the terminals on the outside of the rear of the switch where they were soldered on, or inside where the corrosion caused weak or bad connection and power loss. So I did a little searching for a CB100 ignition switch picture and this is the only one I found. rather than the metal housing with bendable tab areas, it looks like this one has a plastic body and probably slots on the sides where plastic tabs go into the outer plastic case and hold the back of the switch on where the wires are soldered. It's possible that the wires on yours have simply gotten corroded and may be ready to fall off, or if not then the inside contacts will need to be looked at if continuity of the switch is where your power loss is coming from. It's possible you could test by jumping the two wires together since it's a simple two pole switch.

R4L: January 2012

 

[Nordheim]

Actually, I did have this happen when I was a teenager. My Dad and I were working on used bikes for me as I went from a Honda 50 to a 90 and another 90 and along the way, we encountered an ignition switch or two that either had wires corroded off the terminals on the outside of the rear of the switch where they were soldered on, or inside where the corrosion caused weak or bad connection and power loss. So I did a little searching for a CB100 ignition switch picture and this is the only one I found. rather than the metal housing with bendable tab areas, it looks like this one has a plastic body and probably slots on the sides where plastic tabs go into the outer plastic case and hold the back of the switch on where the wires are soldered. It's possible that the wires on yours have simply gotten corroded and may be ready to fall off, or if not then the inside contacts will need to be looked at if continuity of the switch is where your power loss is coming from. It's possible you could test by jumping the two wires together since it's a simple two pole switch.

R4L: January 2012

Fantastic! Thanks for the scoop. I actually think that’s what it was as I fiddled with it for a bit, took it apart, cleaned it and presto! Works again! Thank you!