Motorcycle Repair: Battery runs down when lights are on, honda ct90, volt bulbs

Question
I have a 1971 honda ct90.and it has 12 volt bulbs.will this cause the battery to run down.and if so do i need to get 6 volt bulbs.and where do i purchase them

Answer
If you put 12 volt bulbs in a 6 volt system, they will draw half the current of a 6 volt bulb so that's probably not the problem.  The lights won't be very bright though.  There are only 4 parts in that charging system. The rotor, the stator, the voltage regulator and the rectifier.  The stator is easy to check.  Just measure the resistance between the 3 yellow wires coming off the stator.  They should all have the same resistance and no continuity to ground.  You can check the rectifier too but you have to measure the resistance on one direction and it will be very high.  If you reverse the leads and measure resistance in the other direction it will be very low.  Repeat this procedure on all three wires going into the rectifier. You need a digital meter to see the difference. If those check out okay, it's probably the voltage regulator or a wiring harness problem.  

Regards
Rich