Fordson New Major gas running lean

Fordsoll

Member
Hello, I have a Fordson New Major Gas tractor that will run too lean with no choke. I checked for air leaks using starting fluid, propane and carburetor cleaner and could not find any. I have boiled the carburetor and sprayed every passage out with carb clean and compressed air. My main issue is that the manual says to remove the metering jet I need a special tool, and I cannot get to the main jet without removing the metering nozzle first. This is a fixed jet carburetor so I can't adjust it at all.
I also confirmed that I have good fuel flow from the pump to the carb.
 
I wouldn't worry about removing the jet - between spraying with carb cleaner, soaking, and poking through it with a very thin wire (stripping the plastic coating off a twist tie works well) you'll get that jet as clean as can be. I never remove the jets when doing a carb job anymore - I see no point. Every week it seems there's a posting here (usually on the Ford N forums) by some chap who's tried to remove a jet on his old carb and broken/stripped something trying to get it out. As long as you can poke a wire though and blow it out, it'll be just dandy. But I would make sure you can poke through it: If the gunk is really caked in there, boiling and blowing it out often isn't enough.

I had the same lean issue on one of may new gas majors. The gas majors weren't very popular compared to the diesels, but they are great tractors (I have three). My lean issue was fixed when I rebuilt the carb with new gaskets and ensured the carb halves were mating tightly (I put a piece of very fine sandpaper on a piece of glass and drew the mating surfaces over it a few times to flatten them out and clean them up).

Were you able to get new gaskets for your carb? If so, did you have to make them yourself? Rebuild parts for those carbs are pretty much impossible to come by (another reason why it's best not to risk wrecking a jet trying to remove it). I had a few gaskets kits for those carbs made; I drew the gaskets in CAD and had a local laser-cutting place make a few sets. Might still have one around if you're interested - I'll take a look. But they're not hard to make yourself if you need to.

What kind of adjustments have you done to the main jet to try and make the mixture richer/leaner? I can't remember what the nominal adjustment in the manual is, but I know I had to tweak mine to run properly. Have you checked the torque of your manifold nuts? The nuts holding the intake manifold on often work loose and cause it to suck air right at the block. I have better luck testing for leaks with oxygen than I do with propane/acetylene/starting fluid, and even then it's not always a perfect test. Often a slight leak will be present that's not detected with the old acetylene/propane/oxygen trick. Especially on an open engine like that with the rad fan blowing so much air by it constantly: the propane/starting-fluid/oxygen you're using to test probably gets mostly blown away before it gets a chance to be sucked into the leak.
 
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Manifold gaskets would be my first port of call if the carb has been cleaned. The early carb had an adjustable jet but they soon changed it to a fixed jet. When I had the problem on my petrol/kerosene version it was the manifold gaskets.
 
I put new manifold gaskets on before I posted this and there wasn't much of a change. I had to make a new gasket for my carb, I had already resurfaced one side but didn't do the other because my piece of sandpaper was in the center of the glass and the bend for the intake got in the way. I will resurface the other side and see if it works. The carburetor is also leaking a little bit of gas from the gasket when I over prime it. I will also make a better gasket because at the time I didn't have the gasket material I wanted to use.

Unfortunately It has a fixed main jet but hopefully it won't be an issue once I have this sorted out.
 
I made a new gasket and put some permatex aviation gasket sealer on (light amount). Still wants to run at half choke, I should note that it is missing the air cleaner assembly. Would it restrict it that much? I assume a clean air cleaner wouldn't restrict it like half choke would. I should also note that this thing has a chevy hei distributor on it unfortunately, Does anyone know where I can get something with points that fits this?
 
I had trouble With the idle circuit on the c Farmall , was plugged up not amount of carb cleaner was going to remove it ,it was a .04 hole , that needs a .04 drill to hand twist it .clean it out.
Not famil with what’s on the Fordson for carburetor.
The other thing I do is,I’ll mention ,I put a vacuum gage on the tractor to troubleshoot issues with the fuel and mech issues.
should have 18 to 21 inches of hg on gage with steady needle . If not then it will point out the problem With a troubled chart .
last thing is how the timing ?
 
I rewired the tractor because the old wiring was very bad, and I also did some work on the distributor and as I was setting tdc I noticed that the spark plug is half the length of what it should be. I ordered new correct spark plugs for it and between the rewiring, distributor work, and the spark plugs it should run great.
 

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