2007-2009 Honda TRX300EX TRX300X service manual, Page 102Get this manual
FUEL SYSTEM Start the engine and warm it upAdjust the idle speed at high altitude with the throttle stop screw to ensure proper high altitude opera tionIDLE SPEED: 1,400 100 rpm
When the carburetor has been modified for high altitude operation, the air-fuel mixture will be too lean for low altitude useOperation at altitudes below 5,000 feet (7,500 m) with modified carburetor may cause the engine to overheat, resulting in serious engine damage and increased exhaust emissionsFor use at low altitudes, you should return the carburetor to original factory specificationsReplace the high altitude main jet with the standard type and screw out the pilot screw the specified number of turns from the high altitude setting STANDARD MAIN JET: #122 LOW ALTITUDE PILOT SCREW OPENING: 18 tum out from the high altitude setting TOOL: Pilot screw wrench (0 type) Pilot screw wrench guide