Spark plug cap resistance

Hi Y'all,

Manual calls out these specs:

Secondary coil winding resistance - 10-15 K-ohms

Plug caps - 10 K-ohms

My bike is running normally and I didn't check the coils, but I did check the caps while I was clipping 1/4" off the ends of the plug wires and re-attaching them (a little preventive maintenance). A PO has replaced at least the front caps. The two rears don't have a brand name on them and I don't know if they are original, but they each have about 8.5 K-ohms. The front caps are NGK and are each 5 K-ohms.

I figure, given the wide range of acceptable resistance in the secondary windings, that the spark probably doesn't really care that the fronts and rears aren't exactly the same. But I was wondering if 5K-ohms in the front (compared to the spec of 10) could contribute to ignition noise in the radio - not enough resistance for proper noise suppression. I don't understand noise suppression, so this is a wild guess. Does anybody know?

Thanks,

Jeremy

I don't quite understand it either, but that's the idea. Resistance in the plug wires reduces noise in radio reception. And then after we have thousands of ohms in the plug caps or wires, some get real concerned about super low resistance in the plugs themselves and we have all these fancy, expensive spark plugs. I don't understand that one either. Am I missing something?

The resistors in these plugs caps can be changed. Just unscrew the contact in the end of the cap, and the resistor and a spring will fall right out.

NGK with 5K is correct.