Jockey wheel: amongst two modest sprockets from the rear derailleur that guides the chain on to the cassette Technical Clarification: A twin-cylinder engine is also called a twin or maybe a parallel twin. It has a posh style with two pistons, two connecting rods, one crankshaft and two spark plugs. https://bike-engines61503.luwebs.com/35709237/not-known-factual-statements-about-bike-part-art