R-BIKES R-bikes come in two flavors: Airheads and Oilheads. These two flavors share a basic engine layout in common, the Boxer, and not a whole lot else. They both look like motorcycles, and aside from basic things like wheels and handlebars, aren't too much alike. The Oilheads are clearly descended from the Airheads, but in the same way that a house-cat is clearly descended from a tiger. (I won't hazard a guess which way around that goes.)
The term R-bike comes from the fact that motorcycles of this type are all named as R and then a number, like R65, R100 or R1200. Most of the motorcycles have a suffix, like LS, GS, R, RT, RS, etc. Each of these suffixes has a meaning, usually indicating a body type or trim type based on the same model. For example, an R100 RT is an R100 motorcycle with touring trim on it (big fairing, hard bags, etc.). An R80 GS is an R80 with modifications to make it more off-road worthy (GS stands for Gel?nde/Strasse, which means Field/Street or Country/Street).
RAT BIKEA motorcycle that's been kept running by any means possible, usually with mismatched parts and minimal maintenance.
RECIPROCATING MOTIONReciprocating Motion of an object between two limiting positions. Applied to piston engines because of the limited up and down motion of the pistons.
REDLINERedline is the maximum recommended revolutions per minute for an engine. In cars equipped with a tachometer, an instrument that measures engine rpm, the redline is usually indicated by, surprisingly enough, a red line. Some tachometers mark the redline with a colored sector. Others have two lines: the lower one marking the maximum allowable sustained engine rpm, the higher line indicating the absolute maximum rpm.
REVOLUTIONThe Revolution® engine, Harley-Davidson's first water-cooled engine (V-Twin, produced from 2002 - Current Day).
RICH MIXTURELambda has been selected to identify the excess-air factor used to quantify the spread between the actual current mass Air/Fuel ratio and the theoretical optimum (14.7:1). A rich mixture yields an Air/Fuel ratio which is lower than the theoretical optimum, i.e. 12:1 is a rich mixture.