How to find the Carter YF, YFA carburetor number?
Which means finding the correct kit.
Fuel Inlet System
As shown, fuel enters between the needle valve seat and needle valve to fill the fuel bowl. The fuel flow is float controlled. Accordingly, the fuel level raises the float arm against the needle valve to the point where it seals against the valve seat and shuts off the fuel. As fuel is used by the engine, the level drops slightly, and additional fuel is admitted through the needle valve and valve seat. In actual operation, a fairly steady float position and fuel flow condition exists. The inlet system parts and the carburetor are of all-metal construction, except
the needle valve, which has a plastic tip. A spring separates the inlet needle valve from the operating pin to cushion the needle valve and float operation. An
internal vent connects the fuel bowl to the air horn. Some external venting is effected through the pump lifter link slot in the main body casting.
Fuel enters the idle well through the metering rod jet shown. The low-speed jet measures the amount of fuel for idle and early part-throttle operation. The upper idle air bleed, fixed idle restriction, and lower idle air bleed are carefully calibrated and serve to break up the liquid fuel. The fuel is then mixed with air as it moves through a passage to the idle port and idle adjustment screw port. Turning the idle adjustment screw inward reduces the quantity of air-fuel mixture supplied by the idle system. The idle port is slot-shaped. As the throttle valve is opened more of the Idle port is uncovered allowing a greater quantity of the air-fuel mixture to enter the carburetor bore.
|Carter YF Carburetor CatalogCarter YF Carburetor Manual|
YF Carburetor Identification
When no carburetor number is present, you may be able to identify your carburetor by using the casting number.
|Casting Number||Carburetor Number||Application|
|630||768s, 938s, 951s||Willys|
|630||787s, 964s, 2008s||Chevrolet|
|648||814s, 820s, 833s||Henry J|
|650||735s, 736s, 740s, 741s, 939s||International|
|776||757s, 824s, 876s, 877s, 892s, 2014s, 2098s, 2137s, 2163s||Nash|
Check balls are often placed in the wrong hole, so don’t assume you will find the correct size in the particular hole.
The bigger check ball goes in the main discharge.
Once the check balls are in place you will need to test them to make sure they seal correctly. Use a test fluid, like carburetor cleaner (NOT WD-40), and a small punch to gently hold down the ball on it’s seat and depress the pump in it’s well by hand. If you get a hydraulic lock then you are good to go. On holes other than the accelerator pump simply watch that the fluid doesn’t leak out.
When the check ball isn’t sealing, then you will need to re-size the hole by tapping on the check ball a couple of times. DO NOT use the new check ball for this. It could become mall formed. Use the old check ball if it isn’t corroded or beat up
YF Metering Rod Adjustment
The adjustment below is for early Carter YF carburetors that don’t have an adjusting screw at the top of the metering rod. Most YFA carburetors would have the star type of adjusting screw.
This adjustment is important and should be performed anytime the carburetor is rebuilt, or the metering rod replaced. With the throttle valve seated (this means the idle screw is not holding the valve open) in the bore of carburetor, press down on upper end of diaphragm shaft (C) until diaphragm bottoms in vacuum chamber. On carburetors which have the projection (D) on the pump lifter link, metering rod should contact the bottom of the metering rod well (E), and metering rod arm (F) should contact lifter link (G) between springs and at supporting lug (D). Adjust by bending lip (H) up or down. In the illustration there is a tool that can be used to hold down the diaphragm, but chances are you won’t have one of those and it isn’t that big of a deal to hold it down.
On models that do not have the projection (D) on pump lifter link, the metering rod should bottom in the metering rod well (E) and flat of metering rod arm (F) should make parallel contact with flat of pump lifter link (G). Adjust by bending the lip (H) up or down.
Needle & Seat
Some of our kits have two sets of needle & seats. One will be spring loaded and the other will not be. Try to use the spring loaded whenever possible, especially on off-road vehicles. The spring type of needle & seat keeps the float from bouncing on a rough road, which will allow too much fuel to enter the float bowl.