Carter YF, 1 Barrel Carburetor Problems & Solutions


I have a willys jeep with a hurricane engine using a Carter YF938 carb. I purchased a rebuild kit form your company a few months ago and completed a rebuild and replaced all ignition parts and set timing and dwell. It idles ok but the RPS go up and down in a random pattern and the engine hesitates when accelerating. When I looked into the throat of the carb during idle, i noticed small spurts of gas. It was my understanding that there should be go gas seen unless the accelerator is increased. Additionally, the mixture screw must be screwed all the way in to keep the engine running marginally well. Getting some black smoke out of tail pipe during idle and plugs are slightly fouled with soot. Any advice you might offer would be appreciated, I hate to take the carb to a carburetor shop. Would rather do it myself.


You may have more than one problem going on, but here are some things to look at:

The RPM going up and down and the fact that the idle mixture screw doesn’t change things might indicate a flooding situation. When I say “flooding”, I’m meaning that there may be too much fuel. The black smoke is also an indication of flooding.

  • The gas spurting out the venturi could be due to clogged idle venting. Using thin wire clean out all small passages, blow out with compresses air.
  • Check the float level. Set to specs
  • Test the float – heat up some water and immerse the float. There will be bubbles if the float is leaking.
  • Check the float needle – did you put pressure on it and damage the viton tip? Turn the top upside down so that the float closes the needle. You should not be able to blow through the inlet hole.
  • Perhaps dirt got into the needle & seat. Flush out with silicon spray lubricant.
  • Test the fuel pump pressure and make sure it isn’t too high. Too much pressure will keep the needle from closing and allowing fuel to enter too fast. A new fuel pump is always suspect.

Watch a video about this problem.

I’m struggling with the rebuild, please help.
Looking down into the carb while the vehicle was running, I could see fuel spilling out from the discharge nozzle. I purchased the rebuild kit, and followed the instructions. But I’m just not getting something right, its still not holding fuel. If I fill the bowl and tip the carb slightly fuel still spills from the discharge nozzle. Should it do this?
From searching around on classic car forums, Ive found some great pictures, what I notice is that my carb doesn’t have a metering rod jet? I didn’t take it out, possibly could have fallen out, and it looks like the hole the jet seats in is not threaded. Do they “press in”?
I have pictures if you you would like to see them.
Thank you for your input

 What I’ve done.
I watched your YouTube video for testing the float, mine has no leaks. Replaced the needle and seat, and adjusted the float. (the inclosed photo is before adjustment, the float hangs parallel with the cover).
Replaced the accelerator diaphragm, and adjusted the metering rod with pump depressed, with play at the eyelet. Replaced discharge check weight. Soaked and cleaned idle jet.

  Should there be a ball weight in the air idle bleed passage?  (I labeled that #2)

  I’m running an electric fuel pump; my pressure is just under 5psi.
I turn on the ignition and the bowl fills up, everything hold fine no leaks.  If i tip the carb or open the throttle  fuel spills out the discharge nozzle.

Mike’s Response:

I have never seen a YF like this one. The main jet would be threaded. They are not pressed in. My guess is that this carburetor is made for something off road, some kind of equipment.

When you say fuel spills from the discharge nozzle, you are referring to #5?

Fuel will squirt from this nozzle (squirt might not be a good term), or flows out when the pump is pumped. If it is coming out of it at idle, then check these 2 things. make sure there is a check ball in the bottom of the main discharge, then the check weight. Also check the idle tube between #1 and #2. If anything is clogged fuel will drip out the discharge at idle.

Soaking your parts in cleaner isn’t enough. Ethanol leaves deposits behind and cleaners will not remove it. You will have to run thin wire through all of the holes, especially the small ones. Then blow out with compressed air.

A vacuum leak would also cause the problem above, but it will most likely be a clogged idle circuit and/or idle vent.

As far as the gas spilling over when tipping. That will happen. The carburetor is not air tight and the bowl is almost full to the top so it can spill over to some degree. Sorry it isn’t in front of me so I can only guess at what you are doing.

Customer Response:

Mike, thank you for the education, your time and patience; I really appreciate it! (as does my old truck!)

You wrote, “When you say fuel spills from the discharge nozzle, you are referring to #5?”; Nope it spills out of #4

You wrote, “Fuel will squirt from this nozzle (squirt might not be a good term), or flows out when the pump is pumped.” This is correct, it does this nicely.

You wrote, “make sure there is a check ball in the bottom of the main discharge”; Do you mean #4? This seems to be where my problem is.  #6 has a tapered brass weight. I have no ball in any of the holes. I must have not seen and lost this part? At the bottom of which # hole.

I’ll be heading to the hardware store for thin wire for  cleaning out the holes.

You wrote, “Also check the idle tube between #1 and #2. If anything is clogged fuel will drip out the discharge at idle”; Just so were on the same page, you’re talking about #4? This does sound like what is happening.


I have a 1954 Willys Pick-up with the 6 cylnder L226 engine and a Carter YF 2467 carburetor. Engine starts and idiles fine but runs very rich under a load, going up a hill, etc. When I adjust the idile mixture screw it doesn’t effect the engine runing until it is almost all the way in tight. I am at 7,000 feet above sea level, do I need to change my needle and seat for higher altitude?

Adjusting the idle mixture won’t affect anything but the idle. The fact that you have to turn it in all the way tells me something is wrong. Since you are at 7,000 foot level you probably need to lean out the main jet, but check your plugs 1st. You want the plugs to burn a gray color. Reduce your jet 2 sizes, then try again. You will need to determine what size your jets are currently. Most will have the size, or part number stamped on the jet. Look for 120, then the next numbers will be the size. If you cannot find any number, then measure the jet, using drill bits and converting to decimal.

Carter YF Jets