1981 C70

Discussion in 'The Garage' started by AJs General, Sep 13, 2019.

  1. AJs General

    AJs General n00b

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    Hello,
    I am working on a 1981 C70 6 volt. The problems I ma having the headlight will not come on while the engine is running. The problem is the flasher will work when I turn the right turn signal on but not the left side. I can tap the flasher and it blinks on and off. What could be both of my problems? please help!!!!!!!!!!!
    #1
  2. SmittyBlackstone

    SmittyBlackstone Been here awhile

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    First, check and clean ALL of the grounds and ground paths.
    Make sure the battery is perfect.
    #2
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  3. youkiddin

    youkiddin Adventurer

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    i think your headlight is ac voltage straight from the stator and all other bulbs work off the battery and the batteries don't seem to last real long . make sure the battery is good.
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  4. superscott

    superscott Been here awhile

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    Uhm, should be 12 volts, could be half of your problems
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  5. Beezer

    Beezer Long timer Supporter

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    nope... think its 6V DC except the headlight which is AC. the flasher or it's wire and or socket need cleaning and inspection. flasher may be bad. something is wrong with the left side signal path. start as above, clean the grounds and all connectors. get a known good battery, test the bulbs. if there is no other way switch left to right. the headlight is a separate issue.

    get the engine running and see what voltages the system makes. I don't have a diagram but the generator makes AC and some of that will go to a rectifier and regulator system, then to battery and feed the DC systems. the headlight on these bikes usually have a separate lighting coil. the tail light should be DC off the battery
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  6. muddywater

    muddywater Bless Your Heart

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    I have an 81 and an 82.
    The 81 is 6 volt and the 82 is twelve volt.

    The headlight on the 82 runs AC and basically uses the battery load to regulate voltage (via the rectifier). Anything goes wrong with the battery or related connections and the headlight goes off like a flash bulb. The original sealed beam units are pricey too. An aftermarket reflector with a replaceable bulb is a good idea, at least till you get it sorted out. I added an aftermarket shunt(?) on the headlight made for a battery less dirt bike that is adjustable from 12 to 16 volts. It sends to ground excess voltage to the headlight.....worked well for many years.

    Honda has used a bunch of different charging and lighting systems on the underbone bikes over the years...most are simple yet have compromises in design that cause issues. Plenty of info online if you dig around... as already stated, a perfect battery and sound connections throughout eliminate most problems.

    My 81 electrical system has actually always worked pretty well except for popping every bulb on the bike if I let the battery go bad.
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  7. Beezer

    Beezer Long timer Supporter

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    interesting... no regulator on the stock bike then. I thought they abandoned that type system in the 70s like everyone else. so only a rectifier for DC, and the load (kinda) self balances due to the AC side self limiting (2 pi FL). in that case, everything must be up to par or it will crap. "aftermarket shunt(?)" regulator... yes. dumps the excess to ground. I would add one in a heart beat is that system does not have one. that, and float the stator to get maximum power (then you could run a series regulator!)
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  8. AviatorTroy

    AviatorTroy Long timer

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    I have an 82. Yours is the last year for the 6v system. The battery is critical in these bikes. Fortunately they are cheap. Get a new battery then see how it goes. Turn signal flasher relay is an easy fix but did you check all the bulbs? Headlight I have no idea but some simple troubleshooting with a multimeter should get you there..
    #8
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  9. AJs General

    AJs General n00b

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    Ok Everyone I have it running I do have a Hot battery. I think I have bad flasher. I still don't have a headlight either low are his beam. This is a 6 volt system so the headlight is going to be AC volts is that correct?
    #9
  10. muddywater

    muddywater Bless Your Heart

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    Honda_C70_wiring_diagram.png
    The yellow wire leaving the alternator (coil on right side in pic) goes to the dimmer switch, then the hi and low headlight filament...it is AC.

    With an ohmmeter,

    Check your filaments in your head light.

    Check for output from your lighting coil/yellow wire when running... use AC setting... probably will be 25 or 30 volts with no headlight load.

    Seems like you can bridge your flasher relay, and the turnsignal will come on and not blink, or it will come on and not blink as is.... depends on your flasher failure mode.
    #10
  11. kantuckid

    kantuckid Long timer

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    And of course the model year, as titled, can vary according to date of sale.
    FWIW, I remade the HL on my 6v 70's Honda by silicone-ing a new 6v bulb into the back hole (I created by removal of a bad bulb) in the old HL unit which had the permanent bulb in the unit originally.
    #11
  12. AJs General

    AJs General n00b

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    Hello,

    I am still having problems with the left turn signal. The right one works great. What else could be the problem. I have another flasher and it does the same thing. Could someone please let me know. Could I bridge the flasher and what does that mean.
    I forgot that the lights come on the back one is dimmer then the front light. the lights just stay on.

    Thank you
    #12