Just quit fooling around with it and convert it to 12 volts.
*12V spins your engine much faster and starts it better in all conditions, especially if it is very cold or if the engine has marginal compression.
*12V with an alternator is more reliable and uses a solid state voltage regulator instead of an old fashioned system of points, coils and electromagnets to regulate the charging voltage.
Solid state is better, more accurate, more dependable.
*12V is more forgiving of dirty contacts on/in the entire wiring harness.
*12v is the industry standard and has been for 50 years. *12v allows you to run sprayer pumps, flashing lights, winches and a host of other modern accessories on your tractor.
*12V lights are brighter.
*A 12v alternator will easily put out more amps than an old fashioned generator and vr.
*An alternator will charge at an idle. Generator generally will not.
*A 12v system is safer. For example, Most people know how to jump a 12v negative ground car, truck or tractor. Not many people know how to safely jump a 6v positive ground tractor with a 12 battery without something exploding in their faces or getting themselves run over.
*6v requires bigger, harder to find wires and cables throughout the system. *12v batteries are to be found just about anywhere, are cheaper than 6v and are usually maintenance free.
*12v lets you use electronic ignition easily.
* And last but not least, is this your only 6V machine? What kind of battery is in your boat, motorcycle, your RV, your classic car or even your 4 wheeler or snowmobile if you have them? Why have an odd ball battery that can't jump or be jumped by anything else?