YPVS
The Yamaha Power Valve System improves engine performance at low and midrange rpm. The YPVS features computerized digital control units and the system is cable operated for precision performance. The self-powered system (no battery, powered by the stator) has two self cleaning cycles, which help to prevent carbon build-up on the valves.
The first self-cleaning cycle happens when the rpm reaches 2500 after initial start up. The second cycle happens after the sled exceeds 6500 rpm and then drops below 3500 rpm.