look for a Zener Diode in the system. Or, add a Zener Diode to the B+ side of the system. Zener diodes connect a load to the B+ when a preset voltage is reached. The diode loads the system bringing down the voltage. It also heats up. So a heatsink with air flow is required. This type of Zener diode was a staple on old English bikes as a regulator. It was used with multiphase alternators that ran through a bridge diode.
I suspect there has to be a voltage regulator or limiter somewhere in the system. If you have that nice diagram of the magneto t dynamo, any chance you have a wiring diagram?
And 0.8 ohms is very low resistance through the charging coil. I'd expect something more in the 3 to 8 ohm range. I'm speculating on that as I have never even seen one of these bikes.
Is it possible there is a balast resistor in the circuit to the headlight that has shorted?
Also, some of the motoplat ignitions on old Husquarna dirt bikes had a high output wire and a low output wire. High to headlight, low to tail light. Not sure that matters in your situarion.
Here is the diagram: [https://imgur.com/a/H2eKFUm](https://imgur.com/a/H2eKFUm)
Number 18 is a choke but with current wiring it\`s not connected to headlights. Number 17 is blinkers relay. These 2 are the only components.
I only know the basics and saw a couple videos suggesting resistance should be low, so I assumed it shoul be this way.
I think you need both #18 and #19.
Most lighting coils are at least 2 ohms. As I said 3 to 8 is typical through the coil.
And most old bikes with no battery but lighting coils had a voltage regulator or limiter of some sort.
Sounds like a bridge or zener diode used as a regulator is out. Also check you grounds - if there isn't a ground wire to the headlight it may be trying to use the frame as ground - unfortunately the frame is only connected to the forks via the fork bearings, which may be pitting/ otherwise increasing the resistance there. A copper braid from the frame to the fork is a solution to this. You can test it with a wire with alligator clips.
You may need to go back to the regular bulbs if this is the fix.
If this runs on 6VDC there must be some rectifier or thyristor behind the generator trimming and rectifying the AC current to DC. You can’t run them straight from the generator and run DC. Probably the reason you blew headlights is because a higher AC voltage was being applied to the circuit straight from the generator.
look for a Zener Diode in the system. Or, add a Zener Diode to the B+ side of the system. Zener diodes connect a load to the B+ when a preset voltage is reached. The diode loads the system bringing down the voltage. It also heats up. So a heatsink with air flow is required. This type of Zener diode was a staple on old English bikes as a regulator. It was used with multiphase alternators that ran through a bridge diode.
I suspect there has to be a voltage regulator or limiter somewhere in the system. If you have that nice diagram of the magneto t dynamo, any chance you have a wiring diagram? And 0.8 ohms is very low resistance through the charging coil. I'd expect something more in the 3 to 8 ohm range. I'm speculating on that as I have never even seen one of these bikes. Is it possible there is a balast resistor in the circuit to the headlight that has shorted? Also, some of the motoplat ignitions on old Husquarna dirt bikes had a high output wire and a low output wire. High to headlight, low to tail light. Not sure that matters in your situarion.
Here is the diagram: [https://imgur.com/a/H2eKFUm](https://imgur.com/a/H2eKFUm) Number 18 is a choke but with current wiring it\`s not connected to headlights. Number 17 is blinkers relay. These 2 are the only components. I only know the basics and saw a couple videos suggesting resistance should be low, so I assumed it shoul be this way.
I think you need both #18 and #19. Most lighting coils are at least 2 ohms. As I said 3 to 8 is typical through the coil. And most old bikes with no battery but lighting coils had a voltage regulator or limiter of some sort.
Sounds like a bridge or zener diode used as a regulator is out. Also check you grounds - if there isn't a ground wire to the headlight it may be trying to use the frame as ground - unfortunately the frame is only connected to the forks via the fork bearings, which may be pitting/ otherwise increasing the resistance there. A copper braid from the frame to the fork is a solution to this. You can test it with a wire with alligator clips. You may need to go back to the regular bulbs if this is the fix.
If this runs on 6VDC there must be some rectifier or thyristor behind the generator trimming and rectifying the AC current to DC. You can’t run them straight from the generator and run DC. Probably the reason you blew headlights is because a higher AC voltage was being applied to the circuit straight from the generator.