This is the OS Speed B2103 Type S engine. This 3-port long-stroke engine offers a high torque at mid-low range with a sweet delivery and low consumption. The crankcase, the crankcase cap and the carburetor feature a new design. The new DLC-coated crankshaft has two tungsten counterweights for smooth rotation and better balancing. The B2103 Type S comes with a low–profile cooling head to provide better drivability and also vertical fins on the top to improve heat dissipation. An O-ring between the cooling head and the combustion chamber insert reduces vibrations protect against dirt thanks to a better sealing. The new 22D carburetor guarantees high response and smooth acceleration.