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magneto XLCH seal beam

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  • magneto XLCH seal beam

    The problem Is not with the mag and have rewired by manual trying to keep it all original 12v mechanical regulator and correct capacitor with all correct part numbers was Abel to adjust regulator for out put voltage after warmed up but while on stand and meter on out put side of regulator no steady head light beam flicker at around 950-1000 rpm's idol that dose not bother but when motor is revved to higher RPM's output voltage jumps to 17 + dc volts and have burned out a few Wagner seal beams and the 1157 taillamp and the 1965 wiring diagram is the simplest there is. I have resorted to installing a auto ballast resistor to control the voltage and it works have not been able to figure it out, thought someone has had the same problem and how they solved it?

  • #2
    You need the magneto voltage regulator
    The Linkert Book


    • #3
      The magneto just runs the motor the motor turns the generator separate systems not connected.
      Last edited by silver65; 10-03-2021, 05:52 PM.


      • #4
        Originally posted by silver65 View Post
        The magneto just runs the motor the motor turns the generator separate systems not connected.
        There is a specific regulator for "Magneto" equipped engines. That was what he was telling you, the battery equipped bikes use a different one. It has very different settings.
        Robbie Knight Amca #2736


        • #5
          Originally posted by Rubone View Post

          There is a specific regulator for "Magneto" equipped engines. That was what he was telling you, the battery equipped bikes use a different one. It has very different settings.
          He said he is running 12v. In 1965 & 66 both models used the same Bosch 12v regulator. 1964 was the last year for 6v and the different regulators by model.


          • #6
            The correct style mechanical regulator was the bosch harley part # 74511-65 is the the right/ correct oem part and I have the correct 12V generator regulator and suppose to be the correct capacitor witch I understand is to hold current to only make the the 12v horn work/sound I my be wrong because the horn only works at around 30mph ( no tachometer ) I am beginning to think that this wiring system first year 12v on the XLCH model did not work correct in the first place and only used for two years.
            Last edited by silver65; 10-04-2021, 06:13 AM.


            • #7
              What you are describing is two fold:
              1) few mechanical regulators can be adjusted to give steady light output below 1000-1100 rpm. Try raising your idle speed to the 1100-1200 range. If that doesn't cut it, swap to an end cap electronic regulator for riding and back to the mechanical for show.

              2) The regulator should cut out by 15.5v the fact it's going over 17 says you're not doing so. Ballast resistors "can" deal with this, but they shouldn't have to do so. Again, replace regulator with a known good unit, attempt to adjust, or swap to an e regulator.

              You know the generator works, it's just working too well and the regulator isn't regulating.

              as for the horn, 6v on a 12v system will have it screaming at pretty much any rpm, regardless of capacitor.


              • #8
                Thanks I have a new cycle electric generator that I have not installed yet .But have not been able to find a 6v horn to fit in the 65 OEM horn cover and yes I have tried a 6v horn on a 12v system and they do work. My problem has been trying to get the old system to work per manual wiring diagram without blowing seal beams. I have had the voltage adjusted to cut out at 15.5 volts and 14v but at higher rpm the voltage jumps and the seal beam is only rated for 14.4v. I even thought the motor vibration was making the contacts in the voltage regulator stay closed longer at higher rpm's and allowing the voltage spikes ,so fare the ballast resistor out of a old chevy that would stop the high voltage from the old mechanical regulators from burning up the ignition coil and points has been working harley had to problems with this system. Just bothers me when I can't figure something out


                • #9
                  Your regulator is "jumping" not because of vibration but because of "pressure."

                  The faster you spin the generator the more current (pressure) it produces. If ANY of that excess pressure is fed back into the system you will continue seeing the voltage rise until it hits 50v and 15 amps, then it just melts down. So, if the contacts just slightly allow leakage . . .you have the situation you're describing, but only north of 2500-3000 rpm (50+mph in 4th).

                  So, at this stage, you know the issue is more or less regulated to the regulator.

                  First stop is an extra ground wire from regulator body to known good ground. If that changes nothing -- time to change the regulator.

                  A "hidden" electronic regulator is one of the best upgrades on an otherwise original CH.


                  • #10
                    I have already tried extra grounding for the regulator it's self to both motor and frame and third I grounded the brow that the light is bolted to and have tried two different correct part number regulators with the same outcome and have tried a solid state electronic that I am sure is fried. The only thing I have not tried and am still might is folding a 10 ft. length of wire and put it in the large frame tube from regulator to the line side of the toggle light switch and adjust the length of wire for the correct voltage drop and resistance. Also two correct generators and correct drive gears with the same outcome.


                    • #11
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ID:	295371 Believe it or not after relocating the mechanical voltage regulator to the correct location for the 1965 xlch sportster under the seat with the correct bracket that I got from Jerry the electrical system seems to be working correct without blowing seal beam and stays lit at 1000 rpm idle.The only thing I can think of the 12V regulator mounted at the end of the generator like on some of the 6V prior years was possibly either the motor vibration or the 12V generator electrical field causing the bosch voltage regulator contacts to act sporadic causing voltage spikes and burning out headlights.This is just a what I would like to think is a guess and why the voltage regulator was relocated and isolated away from motor and generator.Don't know the cause but works much better.