O.S.SPEED B21 Adam Drake Edition 2 - Off-Road Racing Engine Combo with T2100SC Exhaust O.S.SPEED B21 ADAM DRAKE EDITION 2 is an evolution of the previous Adam Drake model that was born with the advice of world-class pro-racer Adam Drake from USA. Features: The Bore/Stroke ratio of the Drake-spec engines is 16.4x16.55mm and are unique to this engine (and it’s processor). Newly designed crankshaft for further improved driving feeling (different tungsten balancing). New updated combustion chamber that use an additional O-ring which reduce vibration and seals out most of the dirt that can accumulate around the sleevsd upper/outer edge. The new carburetor also has its locking screw turned around 90 degrees so its much easier to reach/tighten. Two carburetor venturi inserts are included: 6.5 & 7.0 mm Also available without exhaust system Specifications: Stroke volume: 3.49 cc Bore: 16.4 mm Stroke: 16.55 mm Output: 2.61 hp @ 34.000RPM Practical RPM Range: 4.000 - 42.000 Weight: 353 g