1998-2004 Honda Foreman 450 factory service manual, Page 111Get this manual
FUEL SYSTEM Push the jet needle holder in and turn it 90 degrees clockwiseWASHER
Install the diaphragmvacuum piston in the VACUUM CHAMBER carburetor body, aligning the diaphragm tab with COVER the groove of the carburetor bodyHold the vacuum piston up to almost full open so the diaphragm is not pinched by the chamber coverSPR ING ,= ;_ Install the chamber cover with the spring, aligning its tab with the hole in the carburetor, and secure with at least two screws before releasing the vacuum piston