Ballast Resistor

There is a problem with the power supply to the Ballast or the ballast has burnt out..   I had to think about this as ballast systems are a bit confusing!!

Hi Campbell. The bike will run without the ballast resistor, in my experience no damage will be done for a short period. I recommend that you remove the resistor, join the wires. If it runs OK it is the ballast resistor that's the problem, if the problem continues its the wiring. Incidentally I had a ballast resistor go on my Rotary in Spain. I removed it and continued with my holiday until I received a replacement. I now always carry one. One thing you could is is to make the thing more accessible!

Robert...ballast systems are not confusing, they work like this--The systems is the same for most of our 'classic' cars, the system was started in the 1950s (maybe) and even into engine computer/management days.

We have a 12V battery-we have lower voltage ignition coils ie 6V coils on a 12V system. And to make the vehicle work we have to have a Ballast resistor (to drop the voltage from 12 to 6). WHY-When you press the starter the battery voltage available can/will drop to maybe 10V or less. SO with the starter solenoid we 'bypass' the ballast resistor. This means the 6V ignition coil(s) has 10V or lower on it, this 'encourages' the engine to start. When you let go the starter the ballast resistor comes back into circuit and the system now uses the ballast resistor to run on. Bear in mind to employ this system you must have the specific starter solenoid with the connection for the ballast resistor. Running for any time without the resistor will put an extra strain on the 6V coil/s so be aware.

Bear in mind that the early 1970s Commando had this ballast resistor system but NOT the electric starter hence unnecessary parts (to fail) but it was very handy having 2X6V coils so allowing better installation of electronic ignition. (as opposed to 2X12V coils). This was the reason for WHT/BLU and WHT/PPL wires.

Further specific thoughts on your problem. Monitor (test lamp or meter) the voltage as it appears at your BR. There will be voltage at the output (from the Solenoid, if the engine runs) AND when the solenoid is dropped the voltage should appear at the other end of the BR (hence engine runs).