By-Pass Control Valve

Check by-pass valve shaft for binding or sticking. Check by-pass valve for smooth movement. Check that tab on by-pass valve is in close contact with stopper when by-pass valve is fully open. See Fig 1 .
Check that tab of by-pass valve is in close contact with the full-close screw when the valve is fully closed. If any fault is found, clean linkage and shafts with carburetor cleaner.
If problem still exists after cleaning, disassemble intake manifold and check by-pass valve.

Fig 1: By-Pass Valve Linkage
Courtesy of AMERICAN HONDA MOTOR CO., INC.