Carter W-1, 1 Barrel Troubleshooting

Carter W-1, 1 Barrel Downdraft Carburetor Questions & Answers. As questions are posted about Carter W-1 problems, the question and possible solutions are posted here.

Metering Rod Loose
Carter W-1

The metering rod does not fill the hole. This is normal and under normal operating conditions gas does not spill out this hole. If it is, then there is a flooding situation. There does need to be a washer over the metering rod as depicted in the photo, but it might help with gas splashing out some.

Throttle Shaft Loose
There was some play in the throttle shaft and I’m wondering if that is something you can repair as I’m getting a pretty good fuel leak at the shaft. If you don’t do this repair is there a bushing kit you offer?Gas is coming from the shaft because the carburetor is flooding and gas is running down to the throttle plate and out of the shaft.

Shafts can never be tight enough to seal.

We do not do repairs, but I have a couple of people that do it well. See our recommended companies here.

We do have bushings, but they are sold by size. Don’t know what the W-1 takes as they seldom need it.

Find out why your carburetor is flooding. Once that is fixed the leak out of the throttle shaft should stop.
Flooding caused by:
Too much fuel pressure (probably under 5 lbs on cars that use the W-1 carburetor, but check your motors manual).
Dirt in the needle & seat. This is the most likely problem.
Test the float. If it is leaking, then it will be too heavy and the needle won’t close. Heat up some water just prior to boiling, immerse the float. Any bubbles indicate a leak.

Where do the jets go?

The idle jet is attached to the small plug which goes into the bottom of a W-1’s bowl (as opposed to the very large plug for the accel. pump check valves). The plug which goes in horizontally near the idle mixture screw simply covers a fixed orifice drilled into the casting.

The only “economizer jet” in a W-1 is the main jet (in the bottom of the bowl) as it interacts with the throttle-position-controlled metering rod. This is true of most Carter main metering systems, whether activated mechanically or by vacuum (BB carbs being one exception I can think of).
Hope this helps.

Carter W-1 Carburetor

Concave washer problems

The W-1 uses a copper washer sometimes concaved. If you experience a leak at any of these spots check to make sure the old washer is removed. They hide well and often get missed.

I recently bought a Carter w1 kit. I removed a couple of the screws on the side of the carburetor. It looks like there are brass washers that are pressed into the opening. How do I remove them without destroying the threads in the hole?

Use an awl, or pick to pry up on it. The threads are tough.

  • Question: I recently ordered the K4062 carb kit for my carter W-1 part number 838938 on the brass tag. During disassembly, I noticed all of the brass plug washers are flat not conical. The kit provides 4 conical seals and only one flat. The flat included in the kit was item 31 on the kit’s part list. The rest of the plugs, 4 total have no flat brass washers. The kit parts list seems to indicate that there are conical and flat for items 7,28,31,36, and 39 of the parts list. The kit I received does not have the flat washers included.

Answer: The washers in the kit are correct for the carburetor number it includes. Unfortunately we don’t have any flat washers that I can send you. My guess is that you have copper washers, which would be impossible to find. My suggestion would be to re-use your old washers. Clean then well and for extra measure get some Permatex anaerobic and put a very small amount on both sides of the washers. This will go a long ways to make sure they seal.

Only Runs With Choke Partially Closed
This is due to a lack of fuel, or possibly a vacuum leak.
If a vacuum leak you will probably hear a hissing, or whistling noise. Spray carburetor cleaner around the mount and any other vacuum source. If the idle smooths out, you found your problem.
As far as a lack of fuel, check the following not in any order.

  • Kink, or restricted fuel line
  • Weak fuel pump
  • Float level
  • Float drop – The float may not be moving down enough to let the needle come out of the seat.
  • Float rubbing the side of the float bowl.
  • Test the float for leaking – any fluid or excess solder inside the float will cause it to sink. Heat some water and immerse the float. Any bubbles indicate a leak.
  • Passage plugged – possibly restricted below the main jet. Carefully blow through each passage to make sure the passage is open.
  • Main jet too small – not likely unless it’s a new carburetor for the vehicle. W-1 jets are not available. The old jet can be drilled to a larger size. To make smaller, solder shut and re-drill.
  • Metering rod not pulling out far enough – There is no adjustment, but look at the arm connection to the metering rod to be sure it’s moving up and down as required.
  • Wrong metering rod – If you don’t know the history of the carburetor, the rod could have been replaced with the wrong rod. New rods are not available and unless you have the tag with the carburetor number you will not be able to determine which rod it requires.
  • Restricted air cleaner
Washer at the bottom of accelerator pump well There is a fiber washer which (when new) sealed the brass accel. pump tube to the floor of the casting. I tried only once to replace that washer; BIG mistake!   What I do to ensure sealing is to bead-blast around the bottom of the brass pump cylinder where it joins the iron casting as best I can. I then take some Permatex Threadlocker Green (it is designed to seep in between any tolerance-fit objects); I use just enough that it runs all the way around the outside of the bottom of the pump cylinder. Then I heat it using a Map/Pro gas torch to flash-cure the Permatex, and presto: no more leaks.









Runs Rich









Plugs are black, there is a gas smell after turning off the engine. Follow the idle mixture hole up through the carburetor by blowing air through the passage. Air is carried to the idle mixture and mixed with the gas. The passage may be plugged.  


It is important to separate flooding issues from heat soak, or percolation.

Heat soak and/or percolation can occur when the engine gets hot and comes to a idle, or off status. The fuel then boils causing it to flood over the top, or perhaps evaporate quickly.

Flooding occurs when too much fuel in getting into the float bowl and floods over the top.

Both conditions above can cause fuel to run out of the throttle shaft. This doesn’t mean the shaft is loose, it is just an easy place for the fuel to run out.

What can cause the flooding:

  • The float is filling up with fuel. Heat up some water just prior to boiling and immerse the float. Any leaks will show up with bubbles.
    • We do carry new brass floats for the W-1 W-1 Float
  • Is the viton tip damaged. Look for any scoring. These are easily damaged when pressure is put on the needle while adjusting the float.
  • Check the float adjustment, both float level and float drop.
  • Did the old gasket under the seat get completely removed. We have seen these get crusted over to where it looks like the carburetor itself.
  • Make sure the gasket isn’t cracked.
  • Look for any cracks around the seat.
  • Test your fuel pump. Should be around 2 lbs, but verify this with your motors manual.
  • Make sure the float bowl vent is not plugged. 
  • Test the Needle & Seat
  • Ridge worn in the lip of the float causing intake needle to bind. 
  • This can ·be smoothed off by using a piece of sandpaper or emery cloth about ¼” wide. Rest emery cloth over the lip of the float by placing your thumb on top of it, pull the cloth through and that will smooth off the lip of the float. Do not use a file for this operation. 
  • Float pin worn or holes in float bracket for float pin worn egg shaped. This will cause float to bobble and cause loaded condition. Replace both.
  • Check to be sure float does not bind in casting. 


The low speed jet needs to fit tight in order to get a good seal. Use a tapered pointed object to push into the opening and re-form it to be opened a bit more so that it fits tight. Be careful you don’t split it. These are not available.

Updated on 04/13/2022

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