I don't think it will work on the 4 strokes. The white wire on the 2 stroke motors is actually an additional winding on the mag coil. The 4 strokes don't have that. What this box actually does is take the 6v from the white wire on the 2 stroke mag coil and bumps it up to 12v. I'm not sure, but guessing the circuit inside the box has a resistor or two so it doesn't steal spark from the engine. Also DRBS, if you checked the amps with a multimeter while the bike was idling, maybe even got the back wheel off the ground and gave it a little gas, it will most likely produce more amperage when the engine is under load. It will most likely go up from one amp to two, possibly even three amps. It should charge a 1.2Ah SLA battery nicely.