Hop on a new Polaris 4-stroke and there is the little yellow PERC reverse button on the left hand control block. You push it, and the machine enters reverse gear. But, wait! Itâ€™s a 4-stroke, how can electronic reverse work? PERC4 is an electronically controlled mechanical reverse (patent pending). Much like the 2-stroke PERC, it is push button activated and provides the ease of use and convenience of PERC; smooth shifting at any incline, and positive locking. This system also features an new â€œPlug-inâ€ driveshaft for simplified maintenance, along with a Vespel chain tensioner for quiet operation.