My coil sparks from the ground

[hopital]

Hello everyone,

I have a lot of problem with my 1970 US 90. I done a lot of test to make it spark from the spark plug but nothing works. Point is good and I have 2 coils.

First test:

Put the coil on frame internal and put back the engine on the frame, check my ground, everything is good. Pull the rope, No spark at all from the spark plug when I ground it.

Done the same test with my ''New old'' coil, no result.

Second test:

Put my coil ground to the engine wth no spark (Picture 1) and tryed to pull the rope, No spark with both coil. I know on picture it look like a nothing but ground were ground.


Third test (accidental):

Put the coil on the engine with nothing else (Picture 2) and pulled the rope. It SPARK but from the grond? I mean it spark from the ground bolt that we use to frame it (Picture 3).



Anyone saw this before? It dont spark from spark plug at all but it spark from ground (bolt)?

Thank you for your help, I really appreciate.

[YTZ drew]

Well, at least you know the source coil makes voltage! Have you changed the condenser? A bad condenser will cause no spark, even with good points, gap set, and good coil. Try connecting a second condenser into the circuit with jumper wires for a quick test, if that fixes it, replace the condenser.

[muthey]

you need to replace the condensor, points can be good all day long but if the condensor is bad it will never spark from the plug. all of my points driven bikes the condensor was bad on, the points were fine. I think out of five of them I only needed to replace one set of points, adjust yes but change just one.

[hopital]

Hello,

Thank you for reply. I don't think it's condensor because I changed it with a new one. I tryied 3 of them.

How can I test electric flow on a non resistor suppressor cap?

Is a resistor spark plug will spark on a non resistor suppressor cap?

Thank you,

[YTZ drew]

After looking at your pictures again, I'm wondering what would happen if you cleaned up all your grounds thoroughly, and tightly connected everything and tried again. The spark at the coil bolt you are seeing is the primary circuit current, and the spark itself is indicating poor contact. As far as the plug goes, I generally use the factory resistor plug caps and non-resistor plugs, but the secondary should still be able to fire with both resistor plug and a cap. That being said, I have seen the old NGK resistor caps go bad more than once. Try another one if you have one, or take it off and see if the bare coil wire will spark to ground.