1976 CT70 Electrical Issue

orangekoi · Jul 6, 2009

I have a potential buyer lined up for my ct70, but after tuning it up, getting a new battery, and having a great time buzzing around on it, I've realized that the turn signals and the brake light do not work.

The tail light works, but when the brake is depressed, the light goes out. When the horn is sounding and the turn signals is turned on, the horn goes out.

Does this sound like a short or might there be another explanation?

I'm considering buying a new wiring harness and seeing if this resolves the issue. Anyone have any experience installing a new harness? Difficulty?

Thanks for any advice!

Henry

Blackwoodz · Jul 6, 2009

Bad ground.....

orangekoi · Jul 6, 2009

Thanks Blackwoodz. I went and cleaned the ground connection under the tail light. Didn't fix the issue. Other suggestions are appreciated.

I've found a new wiring harness here: MAIN WIRE HARNESS CT70 K3_TO_1976 (267V)

$33 isn't bad. Anyone know if there is much to installing one of these? I'm guessing that if there is a short somewhere off of the main harness, this will not fix the issue.

I need to sell this bike and the guy I have lined up right now is definitely interested. Don't know if the electrical issue is a deal breaker, but I'd like to sell this thing completely street legal. Any further help is much appreciated.

FastMC · Jul 6, 2009

orangekoi said:
Thanks Blackwoodz. I went and cleaned the ground connection under the tail light. Didn't fix the issue. Other suggestions are appreciated.

I've found a new wiring harness here: MAIN WIRE HARNESS CT70 K3_TO_1976 (267V)

$33 isn't bad. Anyone know if there is much to installing one of these? I'm guessing that if there is a short somewhere off of the main harness, this will not fix the issue.

I need to sell this bike and the guy I have lined up right now is definitely interested. Don't know if the electrical issue is a deal breaker, but I'd like to sell this thing completely street legal. Any further help is much appreciated.

Could be a short to ground somewhere. Could also just be a lack of nec. current to run all that stuff. You didnt mention your headlight working or not...Does it get brighter when you rev the motor ? That will at least tell you if your AC generator is working. If you have a multimeter, test the voltage at the battery then start and rev the motor to check the charging circuit. Also see what happens to the voltage when you press the brake, beep the horn etc.

If you replace the harness buy it here: Honda Trail Bikes

You'll have to remove the tank from the frame to access all the connections.

orangekoi · Jul 17, 2009

Well guys,

I spent a couple hours today and replaced the main wiring harness in my ct. Everything went smoothly. Tank came out without any issue. Wiring harness was easier to install than I expected. A couple of tight spots, but nothing too bad.

Bad news is that my electrical issues is not resolved. The electricals on the bike act the same way they did before. Only good thing that came out of today was the realization that there isn't a short in the harness.

Here's the symptoms again. The turn signals do not turn on whatsoever. The brake light does not turn on. The headlight (hi and lo) does work as does the tail light. The horn works too. When the brakes are engaged, the taillight goes out. When the turns signals are switched on, the horn will no longer work.

The headlight does brighten when the engine is revved. I have a new 6v battery installed.

Any ideas or suggestions are much appreciated.

Henry

Blackwoodz · Jul 17, 2009

It still sounds like a grounding or lack of good grounding issue to me....did you replace the voltage regulator or stator?

orangekoi · Jul 17, 2009

Blackwoodz,

Is there another ground other than the one under the rear fender? Would you suggest more than cleaning off the corrosion and making sure there is good metal to metal contact?

Haven't replaced the stator or regulator yet.

Blackwoodz · Jul 17, 2009

I do not know that bike or its electical schematics.... but I just know how the lack of a good ground acts.

Sorry I can not be more helpful. Fast MC should be able to give you a detailed layout since I know I have seen his posting of retro fitting that harness in his bike. You really should check the voltage output of your stator at the regulator.

nielspbr · Jul 17, 2009

Stupid question, is the fuse Ok?

makotosun · Jul 17, 2009

Definitely sounds like a grounding issue. The keyswitch needs to be grounded (nice and tight) too.

Another thought is to make sure that the bulb is actually good

Pull it out and connect both poles and make sure you don't have a burned filament. Happened to me . . .

HymieP · Jul 18, 2009

I agree with above posts, sounds almost identical to my problem which was at the ignition and the rear tailight area. Check and double-check, these bikes aren't complicated, you'll find it if you keep digging. Good luck

schofell84 · Jul 18, 2009

check the switches on the handlebars, clean them up and use some dielectric on them. it def. sounds like a ground issue though haha.

cdoublejj · Jul 18, 2009

there should be multiple ground spots and yeah i was thinking the one of the 2 filaments in the tail light might be burnt.

1976 CT70 Electrical Issue

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