O.S. Speed B21 Adam Drake Edition 2 is a update of the previous model, which was conceived with the advice of world-class professional racer Adam Drake. This engine version is the one with the requirements used by Adam Drake to win the big races. It has a 16.4mm x 16.55mm bore x stroke that can only be found in this engine. It has a newly designed crankshaft with the aim of further improving driving responsiveness and feel. It also incorporates the latest engine features, such as an inner head with an "O" ring for improved vibration reduction and dustproof performance, and a carburetor that uses a ball link that makes it easier to adjust the linkage used in the B2103.