500 cc (500SD) belt actuated, desmo valved (V-twin): Almost all motors since 1986. Four-cylinder, gear actuated, desmo valved (V4): (Desmosedici) pushrod actuated, spring valved (V4): Prototype Apollo , only two made. [ edit ] Enthusiasts groups A key part of Ducati's marketing strategy since the 1990s has been fostering a distinct community