1999-2004 Honda TRX400EX FourTrax Service Manual, Page 67Get this manual
FUEL SYSTEM Apply vacuum to the vacuum portThe vacuum should maintainedAir should not flow through the valve ports when the vacuum is applied, and should flow when the vacuum is not applied
THROTTLE VALVE
Remove the three screws, clamp and top coverRemove the O-ring from the body groove
SCREWSAND