Talk:Motorcycle engine

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There needs to be a concensus on the descriptive terms used to describe motorcycle engines. For example most 4 cylinder engines are in-line fours, most Japanese four cylinder engines are transversely mounted (that is across the frame) but others like the Indian, Nimbus and BMW K100 are longitudinally mounted. All however are inline fours as opposed to horizontally opposed fours, square fours or V4s.

The usual description for a transversely monted inline twin motorcycle is parallel twin with inline twin usually being reserved for an engine layout like the Sunbeam S7/8.

Also remember geographical bias when claiming that one layout is the most common. While V-twins may be the most common twin in the US, parallel or horizontally opposed are more common elsewhere.

[edit] Incorrect Engine diagrams

Comment on the engine diagrams: the classic V-twin has a single crank pin shared by both cylinders, not dual crank pins as drawn.Rracecarr 00:53, 11 May 2006 (UTC)

Agreed. The drawing is incorrect, but is there an editor watching this page? Seasalt 04:47, 26 November 2006 (UTC)

[edit] Displacement

Actually two-stroke motorcycle engines can, and hi-performance ones do, have more displacement then cylinder size might suggest. This is due the crank-case acting as a Supercharger-like compressor before intake air is spooled, thus over-filling the cylinder with 'boost' if you will.

turbo-charged engines over-fill aswell ofcource... —Preceding unsigned comment added by 212.187.71.66 (talk) 12:37, 25 May 2008 (UTC)

The pumping displacement is limited to cylinder volumetricity unless a two stage piston is used as most recently used by Hooper. The crank case is only a storage area and it's volume is generally irrelevant to pumping volume. M-72 (talk) 21:39, 25 May 2008 (UTC)

Well allow me to disagree: provided the crank case volume is next to nil - when the piston goes up opening the reed valve fillling a cylinder size of fresh air; and goes down again closing the reed valve and compressing the air top of piston opens spool ports just before BDC, compressed air filles the cylinder pussing out the exhust port(s) a bit, meantime in the crank case new air being more dense opens the reed valve, piston closes spool ports, fresh filling having been pushed out the exhust gets pussed back in by (sonic) pipe backpressure, exhust port closes while underpressure is again filling a cylinder size of fresh air. —Preceding unsigned comment added by 212.187.71.66 (talk) 23:01, 25 May 2008 (UTC)