The cross scavenged engine is a two-stroke internal combustion machine which has a fairly simple port layout. In this type of engine, the scavenge flow normally arises from the crankcase and then flows to the transfer ports in a common duct. Both the scavenge ports and the exhaust ports are often drilled from the exhaust ports side in a single operation. Thus, it simplifies the manufacturing process.
The 'ears' of the deflector are usually centered about a diameter or are set slightly towards the scavenge side.The edge of the ears are usually chamfered at 45 degrees and given clearance from the bore so that they enter the combustion chamber above the tdc point without interference. In a cross scavenged engine, the deflection ratio of the cylinder and piston deflector in the design of the piston crown and the porting is 1.15.
The transition radius of the base of the reflector is not a particularly critical dimension as far as scavenging is concerned and it should be made approximately one third of the deflector height.
Below, schematic drawing of transfer port and deflector plan layout in a cross scavenged engine.
