since magneto driven systems almost always produce inconsistent voltage, and especially with these little engines, the voltage in the white wire can spike fairly high, the only way to guarantee prevention of overloading the led's is to install a voltage regulator. You simply find out what voltage the led's are rated to, and buy a regulator for that voltage. However, if the voltage is too high, it may kill the engine at idle or prevent it from starting, so you will need a switch for the lights as well. I have a 6v headlight with a built in voltage regulator, and it kills my light at idle. I just ordered a mini generator which is basically an extra coil that picks up voltage from the magnet and I will be running my headlight off that from now on.