The voltage regulator doesn't have anything to do with ignition. First things I would check are the ignition coil and the stator. The ignition coil should measure 0.3 ohms on the primary and 8500 ohms on the secondary. The ignition side of the stator, the two yellow-red wires should measure 0.65 ohms. From there check for shorted or loose wiring. You can also unplug the kill switch on the handlebar to check the throttle safety switch.