Turn signals kill engine

Discussion in 'CT90, CT110, ST70, ST90 Discussion' started by Tripod, Jul 12, 2020.

  1. Tripod

    Tripod Active Member

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    This weekend i swapped out a set of bent handlebars for a straight set I just received for my CL70. I unplugged all the connections in the headlight bucket. Unplugged the left and right controls. All pretty simple stuff. Swapped it all over. Now when i have the bike running and i select the Left or Right turn signal, the bike cuts out. It begins to die then run in sync with the turn signal relay.

    Im racking my brain trying to figure out a good way to troubleshoot this one. I double checked all the connections at the bucket as well as the battery. Like i said, it worked fine before.

    By the end of the day, my battery was down to 3 Volts and the bike wouldnt start. Im not sure if I fried the battery or what. Im going to charge it back up tomorrow. Looking at the wiring diagram, it looks really similar to my ST90 or a CT90. The only difference being that there isnt a kill switch up on the handlebars.

    Judging by the wiring and symptoms, it looks like the black wire is getting grounded and killing my coil. Headlight and taillight function fine.

    dratv_2271_158278546.jpg
     
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  3. allenp42

    allenp42 Well-Known Member

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    Do you have the same symptoms when pressing the brake pedal? If everything is fine, I would disconnect the orange and light blue lead in the bucket and try it again. Long shot, but this is just to ensure the TS switch is ok (nothing really crazy like the orange and blue wire, left and right TS- contacts) or wiring have somehow become shorted to each other. This would put a huge load on the flasher and battery.
     
  4. lukelaw1

    lukelaw1 Active Member

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    is the motor original cl70 with oem stator and flywheel? or do you have a cdi?
     
  5. Tripod

    Tripod Active Member

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    Its and xl70 motor with CL70 stator and flywheel. I think its due to low battery voltage.
     
  6. lukelaw1

    lukelaw1 Active Member

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    You are correct, a cl70 powers/charges the condenser via battery and the points opening and closing discharges the condenser and fires the hv coil creating spark. If your battery is low on voltage and the extra current draw via running the turn signals could cause the bike to cut out like the condition you explained. The real work will be finding what is draining the battery or why battery isn't charging while running and driving.
     
  7. allenp42

    allenp42 Well-Known Member

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    I agree that the battery charge level is too low. Short blips of the turn signal should not immediately cause the battery voltage to drop that low. You may want to trickle charge it and try test it with a fresh charge.

    I am not a CL70 expert, but I'm pretty sure it uses one of the coils when the lights are off and the other coil is connect in parallel when the lights are turned on (i.e.: both coils). From some testing I did a a couple years ago, you get a lot of power out of this setup with both coils in parallel. So much so that both coils do not need to be in parallel unless the lights are on or else there is a risk of cooking the battery.
     
  8. racerx

    racerx Administrator
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    You're much more knowledgeable on electrics than I am. If anyone can answer this, it'd be you. That said, as I recall, both coils are part of the same combined charging/ignition circuit and the system is full-wave 6vDC. I would think that Honda did this maximize current output, probably into the 50-60W range (net). Since the CL70 was oriented toward road use and an older audience, real lighting would have been mandatory.
     
  9. allenp42

    allenp42 Well-Known Member

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    Yes, both coils are part of a FWB setup where everything runs off of DC. It may very well be close to 50W. Looking back through my notes, I only tested a CL70 stator under a few conditions but what I what I noted was about 21 watts per coil or about 3.5+ amps dc @ 8,000 rpm. I may retest this winter when I'm tinkering around.

    Regardless, with nothing to limit charge current, I think Honda was on the money by not connecting the 2nd coil until the lights are on.

    I am just being cautious with my comment about cooking the battery. Unless you're running WOT for hours at a time, the risk of cooking the battery is very low.
     
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  10. racerx

    racerx Administrator
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    My mental <fuzzy> math is based upon CT70 numbers. Stock HL bulb being nominally 15W, I've guesstimated ~25W total output for the one, dual-wound coil. CL70 used two single-wound coils. I've no way of knowing how the windings differ, how twin coils might interact...and...the ignition, of course, siphons-off some wattage. Still, full-wave is much more efficient and a more usable HL bulb of the era had to be 25W-40W. Thus, to my thinking, 45-50W total alternator output seems like the minimum needed to meet D.O.T. lighting standards in effect at that time. Probably have to load test a running CL70 to get a precise number. Seems my guesstimate might not be terribly far off, though I try to stay conservative...allow some headroom for differences between nominal, assumed and real-world electrical values. (hopefully that made sense)
     

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