Hey my buddy has a yamoto 150cc quad that is always killing the battery. I got my voltmeter out and measured the voltage and it was at 18volts! Im pretty sure that killed his battery because he charged it and it did not charge anymore. When the quad is off its at 18 volts, when its on it jumps up a lil bit. I disconnected the rectifier and the stator and that did not make a difference. By the way this has a 4 pin cdi box if that makes a difference.

Didnt try to disconnect the cdi because it was kinda hidden and hard to get to, But can that cause it to be at such a high volts? Anything i should look for? thanks.

i don't know if that was a mistake or not but if that is a good reading he is over charging the battery while running just above idle it should be around 13.8 to 14 volts.
then when buggy is shut off and you check the battery it should read around 12.6 to 12.8 thats a fully charged battery.

sounds like the rectifier could be bad i know you unpluged it but it sounds as the damage has already been done.
what about grounds did you check those to.


pud

Haven't checked the grounds, the bike is pretty muddy and dirty so im thinking it might not be getting good contact. I was thinkin maybe theres a short somewhere but f it had a short the voltage will probably be less, ill get into it more tommorrow and see what i find.

Well turns out my reading was wrong lol, my meters battery was dying so it was giving false readings... Turns out it was the rectifier that was bad, Still has a small problem because when the lights are on it reads around 12.30, and when the lights are off it reads 13+. However when the quad is off it reads 11.70. Still got some tinkering to do...

those can be a pain. with the engine running that voltage is fine, when its off it should read battery voltage when measured at the terminals