A Twin cylinder, Parallel twin,inline-twin or Straight-two motorcycle is distinguished from other engines by having two driving pistons and connecting rods to the engine's drive shaft. The cylinders operate with one piston at the top of a stroke while the other is at the bottom of a stroke whether in a two stroke or four stroke engine thus creating a engine balance. Twin cylinder motorcycles can have a single or dual exhaust system. It can be four stroke or two stroke in configuration. In some instances a two cylinder, two stroke can have 2 spark plugs with only one active.