1972 CT70 Fuse Issue

1967 Guy

1967 Guy

Member
I'll try to keep this brief.
After getting my 1972 CT70 running, I decided to clean up the appearance of some wiring from the stator wires to the harness/plug . I got it back together and now I can't stop burning fuses. I disconnected the harness plug and plugged it back in but the same thing keeps happening. I may have put the wrong fuse in at some point (bad eyesight). I realized it when the wires from the battery were getting super hot. Where would be a good place to start troubleshooting? And how?
FYI- engine, gas, tank, and entire wiring harness have all been removed again. Any help would be greatly appreciated!
 
Thank you for the reply, Rick. I'm not super savvy with electrical but I believe I checked all the wires from the stator (and most within the main harness). Everything seems fine and zeros out when checked with a multimeter. Can you walk me through how to check "for continuity to ground on the power wires that I touched at the stator". I'm a rookie.
All I really did prior to the issue was pull the top engine bolt (and a few other things) to drop the front of the motor down so I could untuck the wiring harnesses within the body. May have pulled a bit on the wires but not much.
 
How did you check the wires you touched? What did you check with your multimeter? Set your multimeter to continuity / ohms. Check the end of each wire with the red multimeter probe and the black lead on a suitable ground. There should be no continuity to ground on a stator wire.

You could also have a failed rectifier.

Rick
 
I have a multimeter and alligator clips to check for shorts to ground.
Clip one side of the alligator to ground and the other to your ground (black) lead. Then set to continuity and tap each wire to check with your positive (red) lead. If it beeps, it goes to ground. Double check wiring diagram to see if it should go to ground. If so, happy. If not, short to ground.

Reverse the alligator and clip positive to battery positive lead (no need for the battery to be wired in) to check for short to voltage.

A wiring diagram is vital. Have patience. You'll be okay. Check with YouTube University. That's how I learned.
 
Thank you, both for your insight. I will tinker with it. Was hoping it was a quick-fix... they rarely are. Ha. Just so frustrating that I had the bike running (beautifully) prior to my brilliant episode, now this. I will keep y'all updated.
 
Update...
Rick- My multimeter has a range of settings for ohms (2000k, 200k, 20k). I set the dial to 20k ohms. From what I read/watched, the meter should go to zero (or very close to zero) if continuity to ground. I checked almost all wires in the entire bike. All seemed fine.
I watched a video on "no spark" from "eastcoastish" about how to check the stator components that affect spark. My problem (or one of them) was at the black wire that goes to the primary coil on the stator from the condenser. The wire was fried and broke free of the coil. Yay! Identified problem! I'll replace the stator components (coils, condenser, points).
Also, I checked the "main" coil (not in stator) as described by another Youtube video. The guy stated that the reading should be between 9 and 11 ohms of resistance. Is this correct? Mine is reading 16.25. Should I replace my coil as well? Anything else?
 
the black wire to condensor is for ignition, not sure if that is going to solve the blowing fuse issue, the other coil is the one that generates ac power then goes to the headlight and also the rectifier (converts ac to dc) then to battery. check your rectifier to confirm it is good. should have continuity one way but not the other, continuity both ways is a bad rectifier, for the ignition coil id see if you have good spark at the plug, they rarely fail.
 
Ok. Thank you. I had already checked the rectifier. It is good. Only showing continuity one way. I'll check for spark at the plug next (after I fix the stator). Does it offer any new insight to know that the fuses are/were blowing when I turned the key on. Wondering if the key on, with black wire being bad could have been my issue?
 
Yes. I believe so. However, I DID replace the wiring harness, battery, and coil about 4-5 years ago. The wiring harness and coil are the same as the old ones, but new. The motor, ignition, rectifier all all original (as far as I know).
 
ok, just confirm that the wires on the key switch plug match the plug at the harness, then look at the back of the switch to confirm that the solder points are not touching/shorting out.
 
I have confirmed the wires match at both ends of the ignition plugs at the harnesses and the solder points are not touching. I have also checked the ignition switch with a multimeter to see if it is functioning properly. Key OFF = continuity with blue wire only. Key ON = continuity with black wire only.
I have also checked the coil (Youtube University) and it is producing spark when hooked up to a power supply.`````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````
 
does the new wiring harness have the same wire colors as the old harness.?

check connections in headlight bucket to confirm correct, also don't plug in the rear brake switch or the front brake switch and see if fuse still blows, one of those switches could be shorting by looking at schematics
 

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Double check the battery plug wiring from the battery to the harness. A long time ago I had a leaker type battery ''Parts Unlimited'' with mixed up positive/negative wiring on the plug end of the battery.
 
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All good feedback...
@lukelaw1- All wire colors match up with from one harness plug to the other. I had already pulled the entire wiring harness so I can't check if the wires were correct again, but I know they were bc it was working properly. I rewired the bike about 4-5 years ago and had things running fine. The engine appeared to be running hot, which has lead to 2-3 complete teardowns to try to diagnose the problem. I mention this bc the wiring "shouldn't" be the problem (as far as things lining up/matching), but obviously it is or I wouldn't be blowing fuses.
@OLD CT- Battery plug is correct. The fact that it was working properly then suddenly didn't seems odd. Again, the bike was running. I only experienced issues when I pulled the top engine bolt so I could tip it down to pull the stator plug back out of the body of the frame...then issues (along with putting a 12v fuse in on accident.).
 
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