1998-2001 Honda Fourtrax Foreman TRX450S, TRX450ES Factory Service Manual, Page 102Get this manual
FUELSVSTEM Push the jet needte holder in and turn it 90 degrees
clockwise
WASHEI R
JET NEEDl.E
In stal he diaph ragmvacuum piston in the VACUUM CHAMBER carblJretor body,aligning the diaphragm tab with COVER the groove of the carburetor body_
Hold the vacuum piston up to almost full open So
th diaphragm is not pjnched by the chamber coverInstall the chamber cover with the spring, align ing its tab with the hole in the carburetor, and seGure with at least two screws before fal'e asing the vacuum