early seventies. Honda produced the water-cooled V-3 two-strokes MVX250 and NS400. There have been various race bike triples such as Kawasaki KR750, Suzuki TR750 transverse 3s, and Proton/Modenas KR3, Honda NS500 V-3s. Four Four-cylinder engines are most commonly found in a transverse-mounted inline four layout, although some are longitudinal, as in the earlier BMW K100. V-4 and boxer designs, as in the earlier Honda Gold Wing, have been produced. One of the more unusual designs was the Ariel Square Four, effectively two parallel-twin engines one in front of the other in a common crankcase — it had remarkably little vibration due to the contra-rotating crankshafts. Inline four Production of four cylinder motorcycles began with the FN Four in 1905. The FN had its engine in line with the frame; this layout would be copied by manufacturers in Europe and the United States before World War II. In the United States, inline fours made by Henderson and Indian were bought by enthusiasts and by police departments, the latter using them as pursuit motorcycles. The first across-the-frame 4-cylinder motorcycle was the racer 1939 Gilera 500 Rondine, it also had double-over-head camshafts, forced-inducting supercharger and also water-cooled. Since the advent of the Honda CB750 straight-four engine, straight-fours have dominated the non-cruiser street motorcycle segments. The German manufacturer Münch based their motorcycles on four-cylinder car engines. For example, the Mammut 2000 has a 2.0l with a turbo and cylinder heads by Cosworth. Flat four A flat-4 or horizontally opposed-4 is a flat engine with four cylinders arranged horizontally in two banks of two cylinders on each side of a central crankcase. The pistons are usually mounted on the crankshaft such that opposing pistons move back and forth in opposite directions at the same time, somewhat like a boxing competitor punching their gloves together before a fight, which has led to it being referred to as a boxer engine. The configuration results in inherently good balance of the reciprocating parts, a low centre of gravity, and a very short engine length. V4 Honda uses V4 engines in the ST series and VFR series. As for two-stroke engines, there were four cylinders in the smaller classes such as Kawasaki's 125 cc KR3 square 4 and Yamaha's 250 cc RD500 V4 (RZ 500 in the US). Yamaha later raced transverse four TZ500/700/750's and virtually all the bikes in the last decade of the two-stroke GP500 era were