O.S. engine MAX-91FX Owner's Instruction Manual page 10

4. Use hexagon-head brass inlet holder (61FX) or
plug screw (50SX/91FX) to blank off side boss
vacated by needle- valve assembly.
61FX
Needle Extension
Inlet Holder
Needle-Valve
Assembly
Fuel Inlet
Needle-Valve
Assembly
Fuel Inlet
Inlet Holder
50SX/91FX
Plug Screw (50SX/91FX)
Fuel Inlet
Needle-Valve
Assembly
9
Needle Extension
Needle-Valve
Assembly
Fuel Inlet
Plug Screw (50SX/91FX)