1999-2002 TRX400EX Fourtrax Service Manual, Page 73Get this manual
FUEL SYSTEM Set the thrust washer between the valve arm and carburetor body (throttle drum side)Insert the link arm shaft through the throttle link arm, spring, carburetor body, washer and valve arm while hanging the spring ends as shownAlign the screw holes in the valve arm and shaft and tighten the screw with the washer
Make sure that the piston and butterfly throttle valves are fully closedMake sure the clearance between the link arm shaft and throttle link arm is 0.10.3 mm (0.0040.012 in)Adjust synchronization by opening or closing the slot in the throttle link arm