Q: I have a 1990 Kawasaki ZX-10 that I bought new and have put 80,000 miles on. The headlight is really dim but gets a bit brighter if I rev up the engine. I have a headlight modulator that clips onto the back of the bulb. With the modulator hooked up the bulb will modulate, though dimly, when it's not supposed to. More rpm makes the bulb brighter and stops the modulation. If the revs drop, the bulb gets dim again and the modulator starts up again. I had the modulator checked out by the manufacturer; it's okay. Even without the modulator, the headlight is dim at low revs. I've checked the idle speed, replaced the bulb, and checked all the wiring harnesses and the high-low beam switch. I even pulled the alternator and had it checked out. The battery is new too. What's causing the headlight issues?