Arctic Cats have a closed electrical system. All electrically operated items have a wired ground with one exception. The starter motor which gets it's ground from a main cable bolted to the engine crankcase. The bikes grounds also connect to the engine case at the same point as the main cable ground.
The engine is rubber mounted so there should not be a main ground on the frame but some ground could leak if there is metal to metal contact at the motor mounts. but, it won't be constant.
There should be a black plug under the seat and another under the plastic just forward of the handle bars. they have a orange wire and a black wire. orange is switched power and black is ground. This is where you should connect accessories.