7-1SETTING TUNEC700000TUNINGEC710000ENGINEEC711001Carburetor setting9The role of fuel is to cool the engine, and in thecase of a 2-stroke engine, to lubricate theengine in addition to power generation. Accord-ingly, if a mixture of air and fuel is too lean,abnormal combustion will occur, and engineseizure may result. If the mixture is too rich,spark plugs will get wet with oil, thus making itimpossible to bring the engine into full play or ifthe worst comes to the worst, the engine maystall.9The richness of the air-fuel mixture required forthe engine will vary with atmospheric conditionsof the day and therefore, the settings of the car-buretor must be properly suited to the atmos-pheric conditions (air pressure, humidity andtemperature).9Finally, the rider himself must make a test-runand check his machine for conditions (pick-upof engine speed, road surface conditions) andfor the discoloration of the spark plug(s). Aftertaking these into consideration, he must selectthe best possible carburetor settings.It is advisable to make a note of settings,atmospheric conditions, road surface condition,lap-time, etc. so that the memorandum can beused as a reference useful for future.EC712000Atmospheric conditions and carburetorsettingThe reason for the above tendency is that therichness or leanness of a fuel mixture dependson the density of the air (i.e. the concentration ofoxygen in it).AirAir temp. Humidity pressure Mixture Setting(altitude)High High Low Richer Leaner(high)Low Low High Leaner Richer(low)7
