Along with releasing their new Virtus Power .21 on road engine, Novarossi have also introduced two new offroad .21 engines, the Keep-Off .21-4 and the Keep-Off .21-7XL. Similar to the Keep-On engine released last year, the Keep-Off motors sport the patented new main ball bearing which reduces rotating inertia and increases the engines scavenging. The new bearing features a narrower centre bearing ring than the outer ring, the result of which is increased throttle response and a higher top speed. Both motors, a 4-port and a 7-port comes with ceramic/steel ball bearings but are also available with all ceramic bearings.

Source: REDrc