The OS Engines Speed R21 Shimo Edition 2 Nitro Engine is a 7-port engine with a new cylinder liner, which has extra holes to reduce overheating. The cooling head and 8.5mm carburettor restrictor are anodized in a special colour; champagne gold. The crankshaft is modified to meet Takaaki Shimo's preference - a smooth power transition from bottom to the top speed. For the first time, OS Engines make the combination of TR02 (EFRA2165) silencer with MR03-WC manifold to dedicate to this special edition.