O.S. Engines 21VZ-B V-Spec User Manual

Page 13

CARBURETOR CONTROLS

Carburetor Reducer

Needle Valve

Mixture Control Valve

Assembly Screw

Throttle Stop

Screw

Metering Needle

Thermo Insulator

Four adjustable controls are provided on

this carburetor.

The Needle-Valve:

For adjusting the mixture strength when the

throttle is fully open.

The Mixture Control Screw:

For changing the mixture strength at mid

speed and acceleration. (Do not rotate the
screw more than one turn.)

The Metering Needle:
For adjusting the mixture strength at part-

throttle and idling speeds, to obtain steady

idling and smooth acceleration to mid

speeds.

The Throttle Stop Screw:

For setting the minimum idling speed:

NOTE: Readjustment may be necessary,

occasionally to allow for changes in fuel

formula gear ratio or clutch engagement

point.