One important choice had already been made. Honda had dropped the shaft-and-bevel gears cam drive of its first four, the RC160 of 1959, replacing it with a much stiffer central train of spur gears placed between cylinders two and three. To reduce the length of crankshaft able to vibrate torsionally, Honda used a jackshaft to take the drive, not from one end of the crank, but from a gear at crank center to the clutch. This system made crank center into a node, effectively cutting the free vibrating length of the crank in half. Irimajiri adopted this center-drive concept but placed it in Mercedes W196 fashion behind the cylinders rather than between them, allowing a small but useful narrowing of the engine.