I'd get a multimeter, and check the resistor in the sparkplug cap. It's supposed to be 5000 ohms, but heat, vibration and age can cause them to fail. To check it,unscrew the cap from the sparkplug wire, but the multimeter on OHMs(it looks like an upside down horseshoe, the letter Omega).
Set the range on the multimeter on 20K(20,000),put one of the meter's probes where the sparkplug went, and the remaining probe where the sparkplug wire went. If the cap is good, you should get a reading. If no reading, then replace both sparkplug caps.
How old are the ignition wires and ignition coil? If original to the bike, consider these parts beyond their service life.
www.z1enterprises.com
sells coils, sparkplug caps, and sparkplug wires.
Read this:
Ignition Coils And Sparkplug Wire Choices
What came with the bike, were ignition coils that even when new were marginal, add years of cooking under the tank in the stop and go traffic, and the coils will probably fail when hot.
Replacement coils can be bought at
www.z1enterprises.com
I believe “Emgo” is the brand. They also carry the popular Dyna 2.2 and 3 ohm coils, along with replacement sparkplug wires.
Now, you have a choice on sparkplug wires:
1.Copper plug wires with no supression caps (the best choice, but will produce audio noise on Radio’s and TV’s). Not only do the copper core wires deliver better spark, they will also deliver a much longer lifespan - carbon core wires are prone to erratic spark delivery and early breakdown, & short lifespan.
2.Copper plug wires with supression caps (a built in 5000 ohm resistor, that can sometimes fail, like what came with the bike). These should be checked with a multimeter now and then, as heat can cause them to become intermittent.
3.Copper plug wires with no supression caps, but using resistor plugs(the “R” in the plug number).
4.Supression plug wires with no supression caps.
NEVER use resistor plugs combined with supression caps along with supression plug wires, as now there will be possibly three (3) sources of resistance in the secondary windings of the ignition coils, greatly reducing the spark energy.
Another choice is the Accel 3 ohm coils, with a similar, primary(small wire)electrical connection, using ring terminals as the Dyna ignition coils do. Whatever brand of coil you go with, make sure the primary wires will clear the mounting hardware, as the spacers come close, possibly blowing a fuse. Some riders have replaced the metal spacers with non conductive Nylon spacers, reducing the chance of an electrical problem.
7mm sparkplug wires will fit the stock ignition coils(if they have replaceable wires, indicated by screw off caps on the coils with ridges). The sparkplug wires fit into a port with a brass ”Stinger” that goes into the sparkplug wire or lead(the Brit’s. Canadians, and other countries call the sparkplug wires (“High Tension Leads”).
