Resistor plug caps?

I was looking through my Clymer manual and noticed it stated that "'77 and later models use resistor plug caps". The PO of my bike has replaced the stock coils with Dyna greys and the wires are yellow (Accel?) 7mm copper core non-resistor caps. The stock IC igniter and sensors are still in use but the ballast resistor is removed and I installed the WG mod.

Should I be using the resistor cap wires? I recently replaced my plugs with BR8ES (resistor) plugs to cut down on the fluctuation of my Acewell tach. Does this negate the use of resistor caps?

There's no major problem with the bike, I'm just double checking things while working on a small stumble off idle I experience and thought I might replace the plug wires as they look quite worn in places.

Sonny

that stumble could be a few different things.

resistor caps on top of resistor plugs is like double redundancy. it is a choice you "can do" and doing this once cleans up the spark from shaggy to sharp, any more than that and you can guess you are resisting total potential discharge.

Resistor caps serve two purposes from the same electrical effect. By adding resistance to the path from the coil to the spark gap the spark energy builds up a bit more slowly, lasts a bit longer, and decays a bit more slowly. A longer lasting spark will help ensure complete combustion. This effect will also reduce the amount of interference generated in nearby AM radios.

Modern coils are designed to work with resistive wires which accomplish the same thing.

Resistor wires, plugs, and caps were developed to reduce the obnoxious EMI noise that ignitions spew out. In cars, it makes noise in the radio and can also cause electronics to malfunction. The resistance adds electrical damping to the narural "R-L-C" circuit which forms on the coils secondary. The added resistance is in series with the plugs air gap which is a huge resistance anyway, so there is very little voltage loss across the added resistance during the voltage buildup to fire. It does reduce ringing when the plug arcs and the coil dumps it's eenergy.

On a basic motorcycle with points ignition, I don't think you need resistor anything but I doubt it hurts anything either. If you have computer controlled ignition or a radio, I would use the resistor stuff to suppress EMI.

trippivot wrote:

that stumble could be a few different things.

I'm very aware of that. I am just covering all bases.

resistor caps on top of resistor plugs is like double redundancy. it is a choice you "can do" and doing this once cleans up the spark from shaggy to sharp, any more than that and you can guess you are resisting total potential discharge.

So,...no need for resistor caps if I'm running resistor plugs...right?

Just want to make sure before I get new wires.

Thanks,
Sonny

Sonny, I would run either/or... not both. My preference would be resistor plugs, as resistor caps generally use ceramic/phenolic bodies and are susceptible to becoming porous with age and often don't seal against moisture as well as rubber boots. The other side of the coin is,, by using resistor caps & black solid core primary wires, no one will know at a glance you've updated. luck G