slightly offset, but a variation is to have a single crankpin with "fork & blade" con-rods, to keep the cylinders in line. Non-90° V-twins may have offset crankpins to try to reduce vibration. V-twins may be mounted either longitudinally with the cylinders protruding either side, like the Honda CX500 and Moto Guzzi, or transversely, such as Harley-Davidson, Ducati, or Aprilia. Transverse V-twins can raise difficulties in cooling the aft cylinder, and in siting the airbox, battery, aft carburetor, and aft exhaust pipe. Flat-twin In a flat-twin, or boxer, engine the cylinders are horizontally opposed. The boxer has perfect primary balance, and only a small rocking couple, and unlike a V-twin, regular firing intervals, producing very low vibration levels, without the use of counterbalance shafts. They are usually mounted with a longitudinal crankshaft, with the cylinders protruding into the airstream, so that a flat-twin can satisfactorily be air-cooled. Flat-twins are made by BMW and Ural and historically by Douglas, Marusho, and Hoffmann, among others. The longitudinal mounting makes the flat twin highly suitable for shaft final drive. Some early motorcycles used transverse-crank flat twin engines, especially Douglas motorcycles before World War II. Tandem twin The Tandem Twin where the cylinders are longitudinal, and have two cranks geared together such as Kawasaki's KR250 road bike and KR250 and KR350 GP Bikes. A tandem twin is effectively a pair of geared singles, and is to be distinguished from an inline twin such as the Sunbeam S7. Tandem twins are suitable primarily for two-stroke racers. Triple Inline triple Three-cylinder engines, a.k.a. triples, are normally mounted transversely. The British Hinckley Triumph factory has specialized in transverse triples, although their 2,300 cc Rocket III has its engine mounted longitudinally. Other examples are the Benelli' "Tre"and the Yamaha XS750. The Italian firm Laverda made a few 1,000 cc and 1,200 cc triples. Some Laverda Triples had 120° cranks, while some had 180° cranks, essentially three-quarters of a four. BMW made the K75 longitudinally mounted 750 cc triple with the cylinders parallel to the ground. Meriden Triumph developed the 750 cc Trident, from which BSA "badge-engineered" the Rocket-3. Some triples were two-strokes. The Kawasaki triples were produced with capacities of 250, 350, 400, 500, and 750 cc in the 1970s, while Suzuki produced 380, 550, and 750 triples, the last being water-cooled. Motobecane made 350 cc and fuel-injected 500 cc triples with 3 into 4 pipes in the