Cylinder Heads (four-stroke)
Cylinder head design has a significant effect on the efficiency of combustion, and hence the power output of the engine. The head may be flat, in which case the combustion chamber resides within the cylinder and/or a depression in the piston crown, but usually a "dome" within the cylinder head provides most of the combustion volume. In motorcycles, valve gear tends to be side valve, overhead valve (ohv) with pushrod operation, (single)overhead cam, (s)ohc, and double overhead cam, dohc. An ohc (or dohc) cylinder head will have at least two valves per cylinder (1 inlet and 1 exhaust), but some have three (2 inlet and 1 exhaust), or four (2 inlet and 2 exhaust), or even five (3 inlet and 2 exhaust). Cylinder heads are the hottest part of the engine and require adequate cooling, typically air cooling, oil cooling or liquid cooling.
Some motorcycles such as Harley-Davidsons, Moto Guzzis and BMWs become identifiable by their cylinder-head types, namely airhead, panhead, oilhead, and even knucklehead. The Ducati desmos head enables higher rpm to be achieved without detrimental valve float.
Read more about this topic: Motorcycle Engine
Famous quotes containing the words cylinder and/or heads:
“The outline of the city became frantic in its effort to explain something that defied meaning. Power seemed to have outgrown its servitude and to have asserted its freedom. The cylinder had exploded, and thrown great masses of stone and steam against the sky.”
—Henry Brooks Adams (1838–1918)
“He had first discovered a propensity for savagery in the acrid lavatories of a minor English public school where he used to press the heads of the new boys into the ceramic bowl and pull the flush upon them to drown their gurgling protests.”
—Angela Carter (1940–1992)