PROJECT - 1970 CT70 K0 - Lifan 125cc

Discussion in 'Projects/Builds' started by 55Wagon, Oct 10, 2017.

  1. 55Wagon

    55Wagon New Member

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    IT'S ALIVE!!! I finally sorted out the wiring, got my chain and sprockets figured out, modified and installed the 12v horn, and hooked up the fuel lines. A couple of kicks and it fired right up and idled smoothly. I still need to shorten the throttle cable, and I bought the new ferrule already. Since it's 30 degrees and snowing here today, I'm not ready for a road test yet!

    One question for anyone running a Lifan 125. When you check the oil level, do you screw in the dipstick, or just put it in until it just touches the crankcase housing?

    Thanks,
    John
     
  2. racerx

    racerx Administrator
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    The same info source that provided wiring & gearing info should be able to give you a definitive answer on checking oil level. At the very least, they should be able to tell you what the oil fill quantity is, after an oil change. Armed with that knowledge, you can easily see which dipstick position should be used...voila! no more guesswork.
     
  3. 55Wagon

    55Wagon New Member

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    Another question. I wired up my headlight to the AC power, and it doesn't come on until the engine revs up quite a bit. Is this normal? Would it be a problem if I wired it up to the DC 12V lead in the headlight housing? I know it would draw a lot more power, but if the bike is running, wouldn't the charging offset it and still keep the battery charged? Your thoughts?
     
  4. racerx

    racerx Administrator
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    For this, specific, issue you asked the right guy.

    You will get full brightness from the HL bulb...for a while. The charging circuit will be running at a partial loss; only a question of how long before the battery is completely discharged. The simplest options: live with it as-is, or source a smaller (lower wattage) bulb. You may have to test a few different wattages to get full brightness, without the old, dreaded, flashbulb effect at high revs. The goal is to regulate peak voltage by matching current draw to alternator output, using the bulbs as the voltage regulator...as was done originally.


    The potentially migraine-inducing info...

    Your 12V Lifan alternator is different than the OEM 6V Honda setup. Instead of a single, 2-pole, lighting coil, with two outputs, yours will have a radial array consisting of either 5, or 6, poles. If it's the 6-pole flavor, you'll have two series-wired, 3-coil arrays, the end of each array run to ground, the other to the harness, as an AC (+) output. The HL (yellow) & charging circuit (white) each get 50% of total alternator output.. Here's where things turn problematic, for HL power. The AC is fed to a half-wave rectifier. Half of the AC waveform is transformed into waste heat, leaving 50% of input power available as DC output. IOW, the charging circuit gets half the usable current that the HL does.

    So, lets assume 10-12.5W per pole. That sends 30-35W to the HL as AC. The rectifier receives that same amount of current, burns-off half of it, leaving ~15-17W available as DC. Realistically, that leaves you with maybe 10W to feed a HL bulb...and still keep the battery charged. Only ways that'll work are finding a 10W HL bulb, hoping that the battery never drops below ~11V before you recharge it, or only using the HL for short duration(s). With a 12v/5.0ah battery and 30-35W HL bulb, you should be able to get 2-3 hours of usable DC headlight power before the battery is completely discharged. I ran that type of partial-loss setup for many years...imho, it's cheezy. These days, you really want DTR (daytime running lights) for safety. I never ran the HL during the day and never rode more than 45 minutes after dark. Replacing the 1157 tail light bulb with an LED 1157 array will free-up ~5W from the charging circuit...as me how I know this.:whistle:

    The possible fly-in-the-ointment...you may have a 5-pole stator. If so, only two coils comprise the charging circuit, leaving you with 2/3 as much AC feeding the rectifier...half of which gets burned-off as waste heat. Translation, maybe 10-12W total DC current going to the battery, marginal...at best...for DC headlight power.

    If you have a 6-pole stator, then you might be able to use a 5-10W LED headlight "bulb". LEDs need DC current and I've seen LED headlights ranging from 5 to 30W with a lot of flavors in between those extremes. They're all 12v. 5W should be brighter than the stock sealed beam. 25W is brighter than most car headlights. So, a good 10W LED headlight should be a welcome upgrade, provided your system has sufficient charging capacity. OTOH, if yours is a 5-pole stator, best to just order a couple of HL bulbs...5 & 10W smaller than what you have in there now, and choose the one that gives the most light, without turning into a flashbulb when the engine gets within 2000 rpm of redline.
     
  5. 55Wagon

    55Wagon New Member

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    Hey racerx,
    Thanks for the very informative reply! As an Engineer (Mechanical, NOT Electrical), I appreciate the detail in your posts, although some of the electrical detail is a bit over my head... After digesting the info, I think I would like to try using an LED headlight bulb, hooked up to DC, and see how that works for me. I would probably install a toggle switch to be able to turn it off when not needed. I searched good old eBay, and came up with the following as a possibility. It shows that it fits 1980 - 1994 CT70, but I'm not sure why it wouldn't fit my 1970 CT70. Maybe you can enlighten me (no pun intended). I'm guessing that I may need to trim the bulb mounting flange to fit in the headlight housing, but I'm not sure. Take a look when you get a moment and give me your thoughts.

    Best Regards,
    John

    https://www.ebay.com/itm/H4-18W-200...713831&hash=item4b28fe94d5:g:1s4AAOSwtplZ10pf
     
  6. racerx

    racerx Administrator
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    I'm not an engineer, of any kind. Sometimes I portray one on this board...having just enough enough practical knowledge to help guide some and confuse the hell out of others.:whistle:

    The one huge issue with these "balanced" electrical systems is the way the coils are wired. Any coil has two ends. Ours have one end run to ground, leaving a choice between AC and half-power DC, via a half-wave rectifier. The early 6v alternator configuration is a little confusing, because there are two AC outputs; in reality, there are two separate windings, on the same armature...each with one end run to ground. IOW two coils on the same armature. With a 3, or 4, coil array, it's the same as one large coil; one unbroken length of wire, wound (in-series) around each pole of the armature...one end run to ground, the other is AC output. The 5 & 6 coil stators are just two 3-coil arrays (the one only uses two of the three poles), each with its own output.

    If one were to lift the ground, turning it into the second output...known as "floating" the ground...a full-wave (diode bridge) reg/rec could be used and you'd have full power, in DC flavor. Everything could then be powered by the battery, like a "real" road machine. That's the hyuge stumbling block. Reconfiguring a stator isn't the most DIY-friendly of projects. Wiring mistakes have major consequences and it's "trial by fire" (not literally, we hope)...give it your best shot, then hope it works, after everything is buttoned-up. If things don't work as expected, frustration is waiting, eagerly. This scares away a lot of folks and that's probably for the best, an ounce of prevention. Yet, IMO, many could figure this out, with enough time & patience. It's really not the black art it seems. Okay...enough tech lecture, onto biz...

    The biggest fitment issues with LED bulbs are: length, will it fit inside the reflector assembly; base configuration, will it fit the reflector and orient the bulb correctly (so the high & low beams are properly aimed; connector type. That last one is most likely the issue being (sort of) addressed in the listing. The LED array shown requires a 3-prong modular connector and the CT70 has what is more like a flashlight bulb holder. You'll need to adapt your wiring. I'd strongly recommend using a modular connector. Spade connectors could be used but, there's always a chance of one pulling loose and shorting-out. A hard shell, modular, connector makes the disconnection all but impossible...and the recessed contacts add a failsafe.
     
  7. andrewdell19

    andrewdell19 Active Member

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    What harness do you have there? The 12v harnesses that I've seen have the circular terminal connections and not the slip on ones like you have...
     
  8. Michael Johnson Jr

    Michael Johnson Jr New Member

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    Hey there, as a fellow Lifan 125 into a 1970 CT70 was wondering if you could help me out with making all the connections up front in the headlight bucket, not many of the connections match up color wise and I'm having a hell of a time getting everything hooked up how its supposed to be. Any help/diagrams you used to get it all sorted out? Thanks for any help!
     
  9. 55Wagon

    55Wagon New Member

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    Hi Michael,
    Sorry it took so long to respond. I haven't been on this site lately. I used the following diagram to guide me. I don't have turn signals, electric start, etc, so I just ignored quite a few wires... Hope this helps!

    413810139.jpg
     

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