Honda Ct70 6 volt wiring and troubleshooting components

[@megastick9324]

This is one of the best, and complete explanations of tracing a wire harness I’ve seen anywhere. I’ve been doing motorcycle and ATV etc repair for a very long time and I get a LOT of units with wire issues, especially ones where the brother in laws uncles buddy has been in there chopping and splicing. DC electrics, 12 or 6v can be like a puzzle, but you have to understand how it all works together. Finding where someone spliced in, or out , a circuit to try to fix an issue can be time consuming, especially when they don’t understand the basics, like the systems where the motor must be running for the headlight to work. The problem is “ un F ing “ the thing to start with. Finding shorts, opens, bad solder joints or splices etc takes time and patients. This video gives a great understanding of the way to approach the process of elimination. Now some harnesses are so chopped up it’s better off to just replace the entire harness, but many times a systematic approach can noodle out all the issues. Again, time and patience. Of course these also have made me a nice little piece of change over the years or scored me some good buys on bikes when the owner is frustrated and just want to dump it for whatever they can get. Anyway, thanks for posting a thorough and comprehensive path to success for those with the patience to tackle a birds nested mess.

[@syby1112]

You the man.... no mindless chatter ,just a knowledgeable no nonsense video .

[@omiross2848]

You really appreciate your video when you have to deal with such a problem...thanks a lot

[@stevebuckmaster13]

Brian , This video is a life saver , Thank you for posting this ! Awesome

[@ws678ta]

Dam good job Brian. Good information.

[@BB-nn9en]

thanks. great video. straight to the point, no BS.

[@mikeb6431]

Great video Brian! Thanks again for posting this.

[@kevinturco9077]

Good job on the wiring harness instruction.

[@charleswest3008]

Thanks so much. Your video really helped. Cheers!

[@chadriddle3517]

Excellent demonstration

[@flyboyslc1]

Great video. I have a Feb of 1971 ct70KO. The old harness showed bare copper, so I bought a new one, I thought correct? I have spark at the plug, and the bike runs great without the battery connected. When I connect the battery, the bike immediately dies. I think I need to remove the new harness and verify wire colors at the switch connector. If you are still monitoring this vid, I would appreciate your input. Thanks.

[@yorkymotogarage561]

Yes I would start there first to verify . Make sure it’s a ko harnes and ko switch

[@flyboyslc1]

@@yorkymotogarage561 You do a great job of monitoring your video. I know from my own experiences monitoring mine, that that is not easy to do sometimes. Thanks for your dedication

[@flyboyslc1]

My friend. I took the new replacement harness out of the bike. Wire colors at the switch connector match. Old harness on the workbench next to the new one. Using ohmmeter and checking wire continuity, as everything is black taped up. Both harnesses check the same EXCEPT that at battery connector black wires. On old harness clipping ohmmeter to black at switch connector and touching other lead to battery black, one has continuity, other black does not. On the new harness doing the same thing, I have continuity at both black wires at the battery connector. It seems like perhaps I have a defective or wrong model harness?

[@yorkymotogarage561]

@@flyboyslc1 could be a very good possibility I’ve had bad ones before

[@PaulRalston-u6l]

Brian - Just found this video on your troubleshooting wiring. Got a 1971 CT70 KO and when running the tail light is on, but when brakes are applied the tail light goes off. Any suggestions on what to look at?

[@joeylatulippe4723]

Great video i'm looking for a ignition switch for a 82 ct 70 do you know where i might look? the switch was missing when i bought it

[@yorkymotogarage561]

Hard item to find . The don’t have a remake for those . eBay is you best chance or try my bike group :Honda ct70 and ct70h only.

[@wildman3541]

I have a 1981 Honda CT70. I'm installing Brand new Honda clutch adjustment bolt. My question is: I have new adjust. bolt, washer O-ring. As for the O-ring - would the O-ring be behind the bolt on the OUTSIDE. The old one was there but doesn't always mean it is correct. Don't' want to crush the new O-ring. In my Clymer manual it does Not show that specific O-ring. Thanks Wildman

[@yorkymotogarage561]

Yes behind washer on outside of cover

[@Goomer]

Excellent video Brian.

[@tomcahill8506]

Brian, i'm finished restoring a Honda 50 C100 1965 and have installed the harness. I would have tested everything had i come across your video sooner. Two questions , do you have to ground the tail-light, front light ,H.T. coil . Is one ground enough . It shows multiple grounds on the wiring diagram. Great video . Very helpful. You would make a good teacher on this subject. Like in your video do the tail light and brake lights come on only when you turn the switch to position 1.

[@yorkymotogarage561]

Yes any light should be grounded if testing unless ground is built into the fixture itself , or it will use the frame as the ground.

[@yorkymotogarage561]

The frame acts as the structural ground but if the light is not working make sure contact points from light to frame are good and clean so that they get good connection.

[@northwesthondact1482]

Excellent well done video

[@Lucy4r]

Hey Brian! I found your video super helpful. I got a 1976 CT and I am wondering if the headlight will work without the engine running? The brown/red wire that the headlight and speedo light plug into doesn’t seem to be getting power and it seems like they should be on the second turn of the ignition.

[@yorkymotogarage561]

Headlight does not work with the bike not running it has to be running for the headlight to work it runs off the stater

[@Lucy4r]

@@yorkymotogarage561 I get power to the red wire on the harness when the ignition is turned once. That gives power to my neutral switch, horn and front brake switch. My tail light will work on the second turn on the ignition. Does this sound correct?

[@yorkymotogarage561]

@@Lucy4r yes

[@kungfu2toe]

Thanks Dude very good video

[@mikekeck7154]

Hi Brian, Thanks for doing these videos they are very helpful. I am restoring a 1972 ct 70 and the 7 amp fuse blows as soon as i turn ignition on. could the ignition switch be the wrong one? I bought the bike non running this is one of many problems to figure out

[@yorkymotogarage561]

Absolutely !!!check wires where they plug together at the switch and harness connection.. Make sure wire colors match . Red to red blue to blue etc. if it doesn’t it’s the wrong switch.

[@mikekeck7154]

@@yorkymotogarage561 Thanks!

[@mikekeck7154]

@@yorkymotogarage561 My ignition switch has a blue wire ( #6) and the harness has a red /white wire in that location. Thank you for this info it was driving me crazy trying to find a short that blew the fuse immediately.

[@yorkymotogarage561]

Yes or a short in wiring . Take tank out and inspecting below tank . Mice chew on them

[@Brad_Jenkins]

Is there a 12 volt conversion kit?

[@robseton7618]

I have a 1978 ct70. The ignition has only two positions on and off, I don't have voltage on the yellow wire at the back of the ignition switch when the motor is running, what could be the problem?

[@cainbeeping8480]

Thanks for sharing brother.

[@scalecraft4663]

Came here to see if the head light on 71 sl rebuild comes on without the engine running. Looks like no. Like my 74 Mt 125. Same deal. Thank You.

[@yorkymotogarage561]

It does not . Only when engine is running

[@jimmorton1169]

Thanks man very helpful

[@brianworden7022]

I have a K0 and the lights only work when the engine is running.. but the horn will work off the battery and was wondering if that is normal or are the lights that aren't related to headlight supposed to run off the battery?

[@yorkymotogarage561]

Taillight ,brake light , horn run off the battery . Headlight runs off the generator when bike is running only in the second switch position

[@jimmcmahon3248]

I tested light as you showed and everything worked. Put everything back together and now it doesn’t work. Do I need a new high/low switch?

[@yorkymotogarage561]

Sounds like it . Can you bench test switch like shown?

[@yorkymotogarage561]

Bike has to be running for headlight to work and Ignition switch must be in the second position

[@SpeakerKevin]

Thanks for posting.

[@TonyWie-db2ns]

I need help with my blinkers 6 volts 74 ct70 Checked out bulbs have new switch made sure orange is right side blue is left side

[@yorkymotogarage561]

Grounding is. Crucial for them to work . Also have to make sure you have a functioning blinker.

[@richardmarquet4500]

Help needed ct90 ko 68 model will not spark unless i touch coil to the motor , when bolted back in place under the tank no spark or very rarely but not enough to fire it up where would the bad earth be doing my head in looking for it , would it be the motor to the frame not having a good connection or does it earth elsewhere on the harness it has new coil , battery , points ,timing is correct , just finished total motor rebuild and the bastard wont start ! just about ready to burn it !!!!!!!!

[@nickf8524]

What's your opinion on when headlight is on taillight goes dim?

[@yorkymotogarage561]

Sounds like a grounding issue . Make sure you have the proper 6 volt and not 12 volt bulb and make sure taillight bracket is grounded to frame with a ground wire

[@seanfane8786]

QUICK QUESTION BRIAN , HOW DO I KNOW I HAVE THE CORRECT HARNESS TO BEGIN WITH ? I HAVE BEEN WORKING ON MY FRIENDS 71 CT70 AND CAN NOT GET ANY POWER TO THE TAIL LIGHT . WE WATCHED YOUR VIDEO ON MATCHING THE IGNITION WITH THE HARNESS BUT IM NOT SURE IF ITS THE CORRECT HARNESS.

[@yorkymotogarage561]

Ricky Beeninya make sure wire colors on harness match wire colors on switch where they plug together.If they don’t match it’s not correct . Ko has a different switch and harness than the k2-78 bikes.

[@yorkymotogarage561]

Insufficient ground . Run a wire from frame to taillight housing and se if it lights up

[@yorkymotogarage561]

Check for dirty or insufficient ground contact . The lights have to be grounded properly to work.

[@chrishaan5766]

On the tail light you forgot to mention green is grounded to the fender The other two wires are tail light and stop light Bulb may not have been bad

[@MrRojoneck]

14:20

[@trunksfan101]

Brian.. My ct70 headlight gets brighter when the bike throttling up.. Dim when the throttle down... Is this a stator issue??

[@yorkymotogarage561]

It’s typical Honda headlight system . Make sure your battery is charged so it won’t blows bulbs . Old Honda’s were known well for their crappy 6 volt weak system .

[@TheDatpussy]

No that is completely normal

[@davidbisnette7673]

What is causing my headlight and speedo lights to burn out, checked a/c voltage at headlight build at wide open was 7.9 volts , I guess I have a 12 volt bulb in the brake light, any ideas are welcome

[@yorkymotogarage561]

Make sure that your rectifier is working properly and battery is fullycharged . Your battery works as a buffer to level out voltage spikes .

[@davidbisnette7673]

@@yorkymotogarage561 Battery is fully charged, I installed a new plug in diode rectifier , this being a 79 has signal lights on it also, which the bulbs remain good in those, so not sure where to go from here, Thanks for any additional suggestions, I do enjoy you videos

[@davidbisnette7673]

@@yorkymotogarage561 7.9 volts is that within the limits of a 6 volt system or is it excessive, could the lighting coil be damaged? Allowing to much voltage? Where the diode rectifier plugs in the connectors appear to have heated up at one point or another, could a lose connection there cause the issue?

[@yorkymotogarage561]

@@davidbisnette7673 my next recommendation would be to check the stator and it’s wiring for shorts and possibly consider replacing the charging coil.

[@davidbisnette7673]

@@yorkymotogarage561 I will give that a try, I actually wonder if someone before I have owned it may have tried to jump it off with a vehicle , from where I dragged it out of it certainly could have been a possibility Thank you for your help!

[@TheHillsten]

how many amps?

[@jimginestra9390]

Hey great video but I'm having a problem with my horn it sounds week

[@yorkymotogarage561]

Jim Ginestra there’s a screw on the back . Try to adjust it . It will tune the sound of the horn.

[@jimginestra9390]

@@yorkymotogarage561 thanks I will give it a try

[@skkrump]

that must be a newer harness my harness from a 69 must not have a brake light . don.t see the brake light wires

[@yorkymotogarage561]

Should be a brown and a green wire by itself at the opposite end of the wiring of the keyswitch

[@billyvo658]

Hi can I have your number ask you some question about Honda scooter wiringconnection

[@yorkymotogarage561]

8124989085

[@davidbisnette7673]

This is a 79 ct 70 sorry