Cobra Y173V, Service Manual

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4. DISASSEMBLING AND SERVICING
4-4-6 Carburetor
At high altitude, the standard carburetor air-fuel mixture will be excessively rich. Output
power will decrease, and fuel consumption will increase.
Engine performance can be improved by installing a smaller diameter main fuel jet in the
carburetor and readjusting the pilot screw. If you always operate the engine at altitudes
higher than sea level 1000 meters over, have our authorized dealer perform this carburetor
modification. If not, should lower load power in operating gasoline engine.
Even equipped with suitable carburetor, engine horsepower will decrease approximately
3.5% for each 300 meter increase in altitude. The effect of altitude on horsepower will be
lowered greater than this if no carburetor modification is made.
If a carburetor suitable to high altitude is equipped with engine suitable to a lower altitude,
the lean air fuel mixture will make engine output power lowering, over-heat and seriously
damage.
The gasoline enters into the carburetor from the fuel tank and fuel filter. The fuel filter can
filter the foreign matters in the gasoline and oxide out of the fuel tank. If having quality
defectiveness, partly foreign matters will enter into the carburetor. Otherwise, the gasoline
contains some composition which can form the colloid after long sediment, and attach in the
carburetor parts (such as main jet) oil path and float chamber surface. The air enter into the
carburetor. Through air filter, based on the intake can not be too much resistance and other
factors to consider, the filter can not be too dense and therefore part of the air in the tiny
impurities will enter into the carburetor through the air cleaner.