Eton IXL 40 RASCAL & e-ton RXL 40 Viper Jr but not 40e rev limiter/Governor Adjust engine top rpm & speed by limiting ignition fire. note: arrow determines position. turned all the way left is not recommended. 1/4 turn to the right from full left is slowest. all the way to the right is fastest rpm setting. Want max speed? replace factory ignition coil with a Type 1 heavy duty racing ignition coil to avoid grenaded flywheel. then remove this part and trigger module and most important remove the metal tang from flywheel fin. instructional videos on youtube.com on channel SCOOTR.com