Motorcycle Repair: holding a charge 1976 cb 500 t, magnetic rotor, regulator rectifier

Question
Hello, I just picked up a fairly in good shape Honda 76 CB 500 t and the last owner told me that if you ride the bike for long periods of time the battery does not hold a charge even with the new battery. I have not ridden it long enough to experience this yet but would like to know where to start. also the front turn signals stay lit when the lights are on and when i switch the left one on it goes out but the back one works. could wiring somewhere be killing the battery? new stator needed?

Answer
That year had running lights up front.  So the turnsignals were on any time the engine was running or the key turned on.  The running light went out when the turnsignals were turned on.  I'm betting one of the filaments in the front bulbs may be burned out.

There are three parts that can prevent the charging system from working...the rotor, the stator and the rectifier/regulator. You can check the stator with a volt Ohm meter.  Check resistance between the 3 yellow wires.  They should have equal resistance between them and no continuity to ground.  If they don't pass this test you need a new stator.  Also the field could should not have continuity to ground, if it does, it's bad.  The last part, is the regulator rectifier. but there's no easy way to test this but if the other two parts are good that the only thing left.  

The only other thing that can run a battery down is if you have high electrical demand on the charging system like a rear brake light switch stuck on or if someone has changed the wiring to run more lights than it was designed for.

Regards
Rich

Sorry Eric, I saw the T on the end of the 500 just as I pushed the send button.  The twin had a magnetic rotor and not a field coil. The stator can be checked as I described but if the rotor has lost it's magnetism, there's no check that I know of. I just replace is last.