A straight-three or triple cylinder motorcycle is distinguished from other engines by having three driving pistons and connecting rods to the engine's drive shaft. Typically the cylinder configuration in an inline formation.
The cylinders operate with one piston at the top of a stroke, another in mid-stroke, while the third is at the bottom of a stroke whether in a two stroke or four stroke engine thus creating a engine balance.
Triple cylinder motorcycles can have dual or a triple exhaust system. The exhaust pipes can merge just after exiting the cylinder head as in Triumph motorcycles or can be three independent pipes as in Kawasaki motorcycles.
Motorcycles using a triple cylinder configuration: