Coil Burnign up

[Zedx]

In the process of building a 77 CB750 café. I ditched the wiring harness and made my own from scratch. Got it all hooked up bike ran fine for a few minuets it stalled (needs carb work). Bike sat still in run position for about about 15 min and started to hear popping from the coil, it got so hot it melted some of the casing. Needless to say it is now fried, does anyone know why this happened?

Could it be that I was using a marine battery for testing?

I bought new plug wires from Dime city and use the plug caps that it came with and am unsure if there is a resistor in there. How important is that? Is there resistors on those Dyna wires?

The coils were mounted to a freshly painted frame and don't think it was properly grounded could that be an issue? Do they have to be grounded?

Please help I have new coils on the way and don't want to blow another $70, I'm poor.

 

[HerrDeacon]

Bike sat still in run position for about about 15 min and started to hear popping from the coil, it got so hot it melted some of the casing.

This is most likely the reason, you had current going into the coil for 15 minutes causing it to heat up. If the bike is not running shut it all off.

 

[Zedx]

Ok good to know and thank you. Do you know how vital it is for the coil to grounded to the frame?

 

[Bert Jan]

Ok good to know and thank you. Do you know how vital it is for the coil to grounded to the frame?

No ground is no go. The circuit needs to be complete.

positive wire into coil, plug wire out to plug. plug grounds to engine. engine grounds to frame. frame grounds to coil. voila.

Its strange the coil melts when a battery is put on. Did you use the original coils or aftermarket stuff?

 

[Rich Ard]

coils on that bike do not ground to the frame

 

[mydlyfkryzis]

The ground for the coil is through the points on the primary side, through the condenser for the secondary. A high voltage pulse passes through a condenser like it was a solid piece of wire. Steady DC does not pass.

The coil itself is not grounded other than the points and condenser. If the condenser ground is weak, that will also cause issues.