I just bought this quad for my son and I'm having some odd issues with it. When I went to pick it up the previous owner said the headlight didn't work. He starts it and its working fine, OK good deal. We try to take it off choke and it dies. OK, I can clean a carb not worried about that. I get it home and try to mess with it and the battery is about toast. I put my trickle charger on it and check it a day later. The headlight will come on but the brake light will not so it won't let the starter engage to turn the quad over. Its just spinning in there. The battery is still weak so I get a new parts unlimited battery and put it in. Turn key onand the brake light is instantly lit. Hit the start and the quad fires after a couple hits and then dies. Now I have no headlights. I've done some searching but haven't found much. Basically is there a correlation to the older battery and low voltage compared to the new battery with higher voltage and why the lighting is acting up?

 

Sounds like voltage regulator is not working , voltage went high and burbed light bulbs out . Old battery didn't have enough voltage to excite the alternator , new battery had enough to excite it and output voltage went unregulated { high } .