Abstract: A multicylinder two-stroke cycle internal combustion engine (10) comprises an individual crankcase cavity (18) for each cylinder to receive the incoming air charge for that cylinder and a cylinder block (11) with at least two cylinders having cooperating crankcase cavities (18) provided with valve controlled intake ports (19) in a common wall (31) of the cylinder block (11). An air induction manifold (25) is detachably mounted to the common wall (31) to form a single air induction cavity (27), at least part of which is formed within the cylinder block (11), and has a single main inlet port for regulation of air inflow to the induction cavity (27). Individual passages (33) communicating each crankcase cavity inlet port (19) with the air induction cavity (27) are formed in the manifold (25). Acceptable performance with limited increase in the overall physical dimensions of the engine (10) can thus be obtained.