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  1. #1
    Super Moderator kirkn's Avatar
    Join Date
    Sep 2008
    Orlando, FL

    6-volt vs. 12-volt coils?

    OK, will '12-volt' coils (standard early 70's points-type ignition) work on a 6-volt bike?

    I once had a Honda CM185 Twinstar, and it was a 6-volt bike and some previous owner installed a 12-volt battery. Popped all the lights (which is how I got it for free!), but the bike ran just fine. I replaced all the bulbs with 12-volt bulbs from junkyards and it was months later before I even realized that it wasn't originally a 12-volt bike. Put over 10K miles on it just fine.

    But what if, say, I have an early 70's Honda SL125 (6-volt) and I try to use a 12-volt coil off some other bike, say, the Yamaha 650 coils Bill bought and used on his 450?

    It seems to me they should work fine (although maybe not 100% up to the design engineer's specs). I mean, the current flows thru the coil thru the points just the same and when the points open, the plug should spark just the same, no?

    Thoughts? Any first-hand experience?


    Current Bikes:

    86 XL250R
    78 CB125 (Lifan 250 project)
    71 SL125 "bitsa"

    Past Bikes:
    too many to name


  3. #2
    Senior Member tbpmusic's Avatar
    Join Date
    Sep 2008
    LaPorte, Indiana, USA

    Re: 6-volt vs. 12-volt coils?

    Wish I could answer that for you, Kirk.
    But I really have no idea.
    Steve is probably the best bet for this type of info - he'll see your post soon.

    Personally, I might have some misgivings about it working right, but that's just me.
    Bill Lane

    '75 CB200T, '71 CB450 K4 Half-Breed, '72 CL350, '81 CM200T, '72 C70M

  4. #3
    Sensei 66Sprint's Avatar
    Join Date
    Sep 2008
    Stephen Lohmeyer,3839 Sun Valley Lane, Roanoke, Virginia 24014

    Re: 6-volt vs. 12-volt coils?

    A 6V battery calls for a 6V coil, .... 12V battery will work with either coil, (although the 6V coil will get quite hot)........ I'm running at 6V (battery, coil and alternator) and planning on using a transformer to get 12V (just) for the lighting... (Love those halogens!)... I'll let you know if it works out..... Steve

  5. #4
    BeKoGe's Avatar
    Join Date
    Oct 2008

    Re: 6-volt vs. 12-volt coils?

    Hi Kirk,

    I think if u use a 12V Coil on a 6V System, the coil will not induct enough High Voltage.
    But I have found ur interesting posting at ... 99410.html.
    I have looked for the Stators of the CM 185 (have 2 from a spare motor).
    It seems that this stators are equal wound to the stator of the SL 125.
    I have messured 0.5 Ohm at the Light Coil and 0.9 Ohm at the Charge Coil.
    The resistance of the Charge Coil is very different to your, I think the resistance (163 Ohms) at the charge coil was to high, may be bad contact or broken wire.

    Bernd from Germany


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