2006-2012 Honda TRX90 TRX90EX/X Service Manual, Page 82Get this manual
FUEL SYSTEM Replace the standard main jet with the high altitude type
HIGH ALmUDE MAIN JET:80
Check that the O-ring on the float chamber is in good condition and replace it with new one if necessaryInstall the float chamber and the carburetorScrew in the air screw the specified number of turns from the factory preset position using the special tool
TOOL: Air screw wrench, type: 07KMA-MS60101 HIGH ALTITUDE AIR SCREW OPENING: 38 tum out from the factory preset position
Start the engine and warm it upAdjust the idle speed at high altitude with the throttle stop screw to ensure proper high altitude operation
IDLE SPEED: 1,600:t 100 rpm (min')