Penta 4-stroke motors Penta made between 1930 and 1937 a very small series of 4-stroke motors. The standard motor was called S-2 and the racing motor was I-2. The effect was 15-20hp at 3200-4500 rpm, 496 cc. and the weight was 45kgs. Penta said these motors were made for professional use. The opposing cylinders is said to give less vibrations. Fuel consumption was low compared to similar 2-stroke engines.