QuestionI have an 1978 XR-185 that keeps blowing out bulbs. They work at low RPM but blow at less than half throttle. Is the lighting coil putting out too much voltage? It measures 36 volts at a few thousand RPM. How are 6-volt bulbs supposed to survive? I measured over 9 volts at the taillight.
AnswerJohn, dirt bikes are really not my specialty, especially when I am looking for a 1978 model that doesn't exist. XR185s were one year only models, built in 1979.
Yes, 6v lights do not survive 36 volt outputs, however, after searching the web for over 15 minutes, I am unable to find a wiring diagram or parts diagram that shows me circuitry or component lists.
My suggestion at this point, aside from telling you to buy a shop or owner's manual at www.helminc.com or elsewhere, is to remove the tank and seat assy, so you can follow ALL the wires from the stator to the harness. Look for some kind of voltage regulator module or perhaps a ballast resistor that is part of the lighting system. The lighting coils in the stator are not regulated by themselves. The faster it turns the more voltage it puts out. Check the lighting coil wiring from the stator through the harness and watch where it may break out for a component attachment. There is a CDI module for the ignition, but there should be a separate little "black box" with a few wires going in and then out to the lighting switch, which feeds the headlight bulb.
If all connectors are clean and tight and any ground wires connected properly, then any modules would be suspect as causes for the over-voltage situation.
That's all I have for you, at this point.
Bill Silver
