THIS sub harness can be used for 6 V or 12 V so you must use a bulb that matches your regulator rectifier. This harness and your 6 or 12v regulator rectifier will only keep the ac current regulated to the headlight (and or tail light) so they don't burn out.. @ SUB-W-4 (S1258) SUB-W-4 (S1258) INSTRUCTIONS FOR JUST NEEDING 6v or 12 VOLT AC LIGHTS REGULATED CLICK ON THIS PICTURE FOR INSTRUCTIONS OF INSIDE BUCKET 12V REGULATING OF CT70KO THRU 1976 HEADLIGHTS @ 12 VOLT REGULATOR RECTIFIER COMBINATION UNIT (214W) (S1070)NOTE!! the yellow wire coming out of the reg/rec never has it's own power,, it just "T's" into the yellow wire that comes from the engine's stator wire, that then goes to the headlight dimmer switch. it takes excess voltage and delivers it back to ground. thus the regulator part of the regulator/rectifier. S1070 @ 6_VOLT REGULATOR RECTIFIER CONVERTS_12V CLONE_ENGINES TO_6_VOLT!! KEEP_ORIGINAL LIGHTS_BATTERY (6V_reg_rec) (S1249)THIS WORKS EVEN IF THE PIGTAIL COMING FROM YOUR NEW ENGINE HAS 12V MARKED ON IT !!!! WITH THIS YOU CAN DO AN ENGINE SWAP AND STILL KEEP THE ORIGINAL 6 VOLT LIGHTS HORN BATTERY AND WELL IT JUST MAKES THINGS EASIER!! WITH THIS REGULATOR RECTIFIER YOUR BATTERY WILL STAY CHARGED MUCH MUCH BETTER THAT WITH THE ORIGINAL HONDA 6 VOLT SYSTEM,, AND THE HEAD LIGHT IS MUCH BRIGHTER TOO, AS THERE IS PLENTY OF JUICE EVEN AT IDLE WITH THE NEW TYPE STATOR THAT THE CLONES HAVE. THIS ONE ITEM CONTROLS THE HEADLIGHT VOLTAGE (AC 6 VOLTS) TO KEEP THE HEADLIGHT FROM BURNING OUT,, AND IT GIVES THE BATTERY PLENTY OF 6 VOLT DC TO KEEP IT FULLY CHARGED AT ALL TIMES.. NOTE!! the yellow wire coming out of the reg/rec never has it's own power,, it just "T's" into the yellow wire that comes from the engine's stator wire, that then goes to the headlight dimmer switch. it takes excess voltage and delivers it back to ground. thus the regulator part of the regulator/rectifier. 6V/reg/rec (S1249)