A cooler motor has a longer lifetime

From holding your shock shaft for an easy shock build

To maintain its racing advantage

'78 and '80

mobility and superior numbers

Team Associated - Reedy Sonic 540-M4 Modified Motor 6.0 Driver Edition Replacement Parts Car and Truck Clutch and Related Parts A cooler motor has aThe 540 M4 Driver Edition is technically identical to the standard 540 M4, but is instead equipped with the popular #27447 rotor. This rotor is the lowest strength option, which is reported to improve throttle feel and consistency, resulting in better overall race times. Four versions featuring the most popular "dirt" winds will be available initially, with the potential for more to follow. All Sonic 540 M4 versions are ROAR, EFRA, BRCA, and IFMAR