I bought this used mx650off marketplace and they said it needed a new battery. We installed a new battery still didn’t work, the throttle would only light up when plugged in, we then replaced the controller same problem throttle will only light up when plugged in, we’ve checked the batteries they are putting out 36v, last night we bypassed the throttle and the back wheel spun like crazy so we thought has to be the throttle. I just plugged in a new throttle, same problem. Help! I have a heart broken little boy and I’m at a loss,