check your grounds and sender. take the lead from the battery and clean it, take where it attaches to the motor and clean it entirely with some sandpaper so its nice and clean, make sure everything is tight. make sure its tight at the gauge and sender as well and clean. the gauges work by sending a signal and measuring the resistance it takes to get to ground through the sender. if you take the sender wire and ground it the gauge will do a full sweep and peg. the fact that its cutting out means you're losing your ground somehow. it could be as much as a bad ground wire as well.
