It requires two open end wrenches.
Use one wrench to hold the largest hex surface (this is what holds the assembly in the carburetor). Use a smaller wrench to loosen the smaller hex surface (this is the adjuster "gland" nut, also known as a lock nut). Once the gland nut has been loosened maybe three quarters of a turn, the "T" handle adjuster should turn.
The gland nut tightens a fibre seal against the adjuster, both preventing the adjuster from turning, and also sealing against a fuel leak.
Once the adjuster has been turned to the required setting, retighten the gland nut.
An approximate beginning adjustment is to turn the adjuster in (clockwise) until LIGHTLY seated; then back the adjuster out(counter-clockwise) two and one half full turns.
Drive the vehicle at highway speed, with a friend following in another vehicle.
If your vehicle surges, the mixture is lean. Back the adjuster out further (counter-clockwise) 1/8 turn at a time. The adjuster is wide open at five full turns.
If your friend notices black smoke, the mixture is rich. To lean, adjust in the opposite direction.
TWO CAVIATS:
(1) ALWAYS use two wrenches to loosen/tighten the gland nut.
(2) NEVER use a wrench or pliers on the "T" adjuster. If it will not turn with your fingers, the gland is too tight. FAILURE TO OBSERVE THIS SENTENCE WILL COST YOU $$$$$$$
Jon.
