O.S. SPEED B2103 TYPE S is a factory tuned engine for 1/8 off-road competition, most parts of which are newly designed; carburetor, crankcase, piston/liner, crankshaft, and inner head. The cooling head is low-profile type, which has low-gravity center with high vertical fins, which contributes to efficient heat dissipation. To say nothing of improvement over its power performance, the inner head with silicon o-ring improves anti-vibration and dustproof performance. The new ball link of carburetor makes linkage adjustment easier.