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Carter YF & YFA Technical

How to find the Carter YF, YFA carburetor number? Which means finding the correct kit.

Some older YF's have the ID number here:
YF Identification

YF Carburetor

Carter YF Carburetor
YF Pump Discharge Check Valve Problem

YF Acceleration Stumble YF-938SA, Willys

Carter YF Carburetor Manual 1968-69
Rebuild videos for the later Carter YFA.

YF Carburetor Identification
When no carburetor number is present, you may be able to identify your carburetor by using the casting number. Keep in mind that the casting number is not definitive. In most cases this is enough to find the correct carbuetor kit, but it's another hint.

Check Balls

Check balls are often placed in the wrong hole, so don't assume you will find the correct size in the particular hole. To figure out which check ball goes in which hole, assuming you have two different sized check balls, look into the bottom of the holes and you should see which hole is bigger than the other. Simply place the bigger check ball in the bigger hole. Be sure each hole has a trough for the check ball to sit into. The check ball has to stop the fluid from going in one direction, so it will need to sit into a beveled edge hole. When there is no bevel, then it probably doesn't need the check ball. 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
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.
What is the size of the vacuum advance port located in the throttle body?
The vacuum advance thread size is 1/8" FPT (female pipe thread), same as the fuel inlet thread.

Carter YF Needle & Seat Height Problem

We have run into a few older YF carburetors that use a shorter needle & seat assembly than what is provided in the carburetor kits. We have added an additional needle to our kits that will take care of this particular problem. This extra needle is included in our basic YF kit K1111 and our YF premium kit PK105

Watch a video about this needle & seat size problem and the solution.

Some YFs will have an old style needle and seat that has a stem and used a filter, these are no longer available. Use the new style needle and seat that is correct for your carburetor number, making sure that the overall length of the seat with the needle in place matches the overall length of the old seat/needle assembly minus the stem. 

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