1999-2002 TRX400EX Fourtrax Service Manual, Page 68Get this manual
FUEL SYSTEM Check the jet needle for stepped wear or damageCheck the throttle valve for scoring, scratches or damageTHROTILE VALVE
JET NEEDLE
ACCELERATOR PUMP
Removethe three screws while holding the accelerator pump cover
Remove the pump cover, spring and the diaphragm, being careful not to damage itVisually check the following: -diaphragm for deterioration or pin holes -springfor deterioration -diaphragm shaft for excessive wear or damageorifice in cover for clogging or restriction