F12 carb adjustments

I have what looks to be the standard F12 downdraft carb but I also noted that it appears to have a third adjustment screw with spring located near the base below the fuel adjusting screw. What is this one for?? I have not seen any references to it although it appears frozen in my carb anyway. It seems to block a port opening near the manifold flange. Rebuild kits do not seem to address this either.
 
Some thoughts for you:

mvphoto32069.jpg

mvphoto32070.jpg

Photograph 1 & 2 show:
Brass fuel adjusting screw and seat (the seat has the hex-head for a spanner on it)
Idle passage plug (24693D). Slot screw head beside brass fuel adjusting screw.

mvphoto32073.jpg

Photograph 3 shows:
Idle adjusting screw (brass with spring near top of photograph)
Idle Throttle adjusting screw (steel with spring bottom left of photograph)
Drain cock (brass bottom right hand side of photograph)

mvphoto32077.jpg

mvphoto32078.jpg

Idle throttle adjusting screw at bottom right.
Venturi lock screw (centre of photograph beside part number disc)
The small, round headed screw below the venturi lock screw is just listed as No. 8-32 x 3/8" Screw, round head - in fuel bowl. It is the one between number 15 and 16 in the cross section of the carburetor.
I think most of that is correct.
SadFarmall
 
The idle throttle stop screw sets the minimum opening of the butterly. Some cars had a hand adjustment for this on the dash board (e.g. Riley Pathfinder) to allow the operator to set a fast idle if desired.

From the Owners Instructin Book, adjustment as follows:
IDLE FUEL ADJUSTMENT
Retard engine speed control hand lever to about ¼ advance. Screw in idle throttle stop screw until the engine speed increases slightly. Now screw in or out the idle fuel adjusting screw until the engine runs steadily. Unscrew idle throttle stop screw until engine idles at desired speed with engine speed control hand lever in full retard position.
SadFarmall
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top