Motorcycle Repair: 1980 shovelhead backfire, ohm meter, shovelhead

Question
-------------------------
Followup To
Question -
Hi, Mike. Thanks for the front wheel info on the 1978 - 1980 FX. My friend has an 1980 FX which keeps fouling plugs after only a couple days riding. The engine has been stroked at some point in the past. He is running a factory Kehine carburetor but has tried a bendix set-up with the same results. we tried hotter plugs and different points to no avail. Any help will be greatly appreciated. Thomas
Answer -
A question for you. The fouled plugs, are they sooty or are they oily?
Mike
re. The plugs are sooty.

Answer
Your problem can be coming from several areas.
One is the carb. If the bike has been doing this ever since he has had it then the jets might be to large for the motor and cause the fouling.
Two is the ignition. When you changed the points did you also change the condenser? Your coil might be to weak. You can test it with a OHM meter. The primary side ( the two posts where the wires connect) should get a reading of around 5.0 OHMs. The secondary side ( the holes where the plug wires go in) should get a reading of around 20,000 to 30,000 OHMs. You could also have bad plag wires.
Good luck and happy riding
Mike