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Discussion Starter · #1 ·
Hi All,

About a week ago I picked up a '73 CB350 that had been sitting since the 80's. The previous owner accidentally broke off the key in the ignition so In wasn't able to see if it turned on or got power but it was a great deal and a very clean bike so I went with it. So I just received a new (genuine used) ignition switch in the mail today, threw it on, and got nothing. I have a brand new 12V battery in there and all of the wires seem to be intact other than the tail lights being gone. I know absolutely nothing about wiring / electricity so I was curious if anyone had suggestions on where I should begin to even look or if I should pull the whole harness out or basically what my best course of action would be. I would prefer to just get it running for now since I don't have much experience with the wiring and then go through it over the winter. Where should I be checking first / are there any common spots that cause issues like this? Thank you for all of the help in advance and I will try to answer any questions I can.

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Do you have a test light or multimeter to follow the power?
Does the horn work? Or blinkers?
Battery is hooked up correctly? And charged?
Battery terminals and cables are clean metal?
Ground cable is grounding?
 

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Attached is the CB 350 Wiring diagram in a Hi-Res format.

You can RIGHT Click and Save-As to a USB and take it to an Office supply shop and have it printed on a large format printer
It makes tracing the circuits a breeze.

Plan Floor plan Text Diagram Technical drawing
 
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Discussion Starter · #6 ·
So I cleaned off the battery terminals to the point where the looked like new copper. That wasn't it. So then I double checked that the grounds were grounded properly. Also wasn't it. So I then tested the fuse which worked fine. After doing those things / also skimming over the wires to see if there were any noticeable / obvious tears in the wires but failed to find any. I then switched my attention to the ignition switch itself. I checked to see if the red wire that has the fuse on it was getting any power to the ignition switch itself. From what I figured out, with the battery connected, that red wire was not getting any power. I did have the ignition switch unplugged just for the sake of testing it which in hind sight could have affected it (?). So then I wanted to see if that red wire had continuity. I was able to run a solid connection from right where it connects to the plug that plugs in to the ignition switch itself all the way back to the battery. Shouldn't it be running power to the ignition switch at all times or did I miss something here? I will throw some photos below to maybe help visualize it incase my explaining wasn't very good. Also if it is something non-ignition related, what are other likely causes? Thank you for all of the help so far. Hopefully we can figure this out and get it on the road! :D
Engine Auto part Motor vehicle Fuel line Vehicle

(Bright red wire with fuse coming from battery is wire specified above)
Wire Electrical wiring Electrical supply Auto part Cable

(Found this split on it but it still had continuity)​
 

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Discussion Starter · #7 ·
Attached is the CB 350 Wiring diagram in a Hi-Res format.

You can RIGHT Click and Save-As to a USB and take it to an Office supply shop and have it printed on a large format printer
It makes tracing the circuits a breeze.

View attachment 197185
Thank you! I was using the photo you sent me on my phone, but I think I may actually go get it printed out because it seems like it would be a bit easier to follow / possibly mark on it what is good to eliminate potential issues. Great idea!
 

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Discussion Starter · #11 ·
So there's a problem with the switch?
Did you check resistance with the key in different positions?
I hope not. I just bought it couple of days ago. I didn't check it with the switch. It was getting late so I gave it a break but I will go and see what I can figure out tomorrow afternoon. Shouldn't there be some kind of current going through that wire at all times wether the switch is hooked up or not since it is coming straight from the battery?
 

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Discussion Starter · #13 ·
No, I don't get any power to the switch. That wire doesn't seem to get any power at all. But then after checking for breaks and seeing if there was any resistance, it all seems fine which is what confuses me.
 

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With one lead on the negative terminal, hook up the red wire. Confirm voltage at the pos terminal. Then before the fuse. Then after the fuse. The at the switch. Then wiggle the red wire and see if it changes.
 

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Discussion Starter · #17 ·
With one lead on the negative terminal, hook up the red wire. Confirm voltage at the pos terminal. Then before the fuse. Then after the fuse. The at the switch. Then wiggle the red wire and see if it changes.
Ok I will give that a shot tomorrow and see what I figure out. I will post an update tomorrow afternoon. Thank you - I appreciate all the help!
 

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Discussion Starter · #18 ·
Ok. So I went and did a little bit more testing on it to see what I could find. Wether the ignition switch was plugged in or not, that red wire does not get any power at all. It has about 12.5v at the terminals but as soon as I go to that wire I get 0. From what I saw on that schematic, it seems like that red wire should be directly hooked up to the battery somehow, but it isn't. Am I correct in assuming this? It is connected to the rectifier but other than that it doesn't hook up to the battery. I am thinking the tear in the picture below is possibly where it was supposed to connect to the battery somehow.
Wire Electrical wiring Electrical supply Auto part Cable
 
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