Leaking needle and seat

[Forward slash]

I bought this old 49 8N some twenty years ago. It's needle and seat were leaking, so I replaced it. It leaked. I've lived with it all this time because I seldom use it anyway. It's truly just for occasional uses, but when I need it, I need it. I would just turn the fuel off and let it starve out. I've decided to go through the old thing since I have more time on my hands and I am after all a factory trained GM tech with ASE master tech certification, and I grew up rebuilding carbs. Went through every iteration of computer controlled carbs and am so glad they have for the most part gone away. Now I've gone through the steering gear box, replaced my brakes and axle seals, painted all the sheet metal, treated it to new light switches, ignition switch, and other refab work. Nice new radiator. And I got another needle and seat for it, but it just leaks like it has always done. Before I went for this latest set, I had used my battery operated drill motor and a 7/32 hex to spin the needle in the seat to get a better seal, and for a few days it worked. I could go out to the shop and cold start it and it would start right up and prove out not to have leaked overnight. That lasted for awhile. So I thought I'd try the third set. No go. I see nothing wrong with the float. It's not hanging up inside the chamber. Does anyone else have this experience and does anyone know of a float that is built with more buoyancy. I took that little spring out that pushes down on the float. I've read posts talking about needles sticking, but I have the opposite problem. I hate to throw parts at problems, but I would sure go for a new float if it would do the trick. Would sure welcome any help out there. Thanks

 

[used red MN]

Hello Forward, welcome to YT! Here is a check that can assure you the needle is seating and all is sealing properly. This is best done when the carb has not been put in service yet due to it can be flavorful. Some brake clean and compressed air should get it back to tolerable. What you will do is invert the carb top with the needle and seat installed and the float. With the weight of the float closing the float valve suck on the fuel inlet of the carb then place your tongue on the fitting to capture the vacuum. It should hold the vacuum against your tongue if it is sealing properly.
I would recommend placing all future queries on your N Ford on the 9N, 2N & 8N forum in the manufactures section.

 

[Tgrasher]

The float could be hanging up on the side of the bowl, check when inverted the side to side play of the float. You can lightly pinch the hinges to true the float and still leave it free to move.

 

[Dieseltech]

Try setting the float gap at 5/16 inch instead of 1/4 inch like the specs say. I've been doing that on the MS carbs lately to stop the fuel dripping and has always worked so far on the MF tractors.

 

[560Dennis]

I might of missed this , but did you test float ? Could it have a hole in it ,full of gas inside float ,will sink when hits fuel .
Put it cold ,get cold , then put submerge in hot warm water and look for air bubbles .

adjustable tang s in float support ,do air low pressure flow test in (like 5 gallon bucket of water) when you get the float adjustment,
i sometimes summerge it in water ,do when this Happen . If it leaks then get back to us. Or talk to carb shop that handles parts. Like YT , mikes carb, McDonald’s in Georgia.

I got a flat surface needle from McDonald Carbs in Georgia for the Farmall Carter Carburetor, been ten years now , talk to them . Might have same for your carburetor ?
Call us back when you find something , helps us

 

[Forward slash]

The float could be hanging up on the side of the bowl, check when inverted the side to side play of the float. You can lightly pinch the hinges to true the float and still leave it free to move.

Before posting, I'd read some threads in here and was ahead of that possibility by checking that it had no problem in that regard. I appreciate the reply. I'm going to be grinding down the old needle to remove weight from it. Just an experiment. As well I'll be taking steel wool to the float in order to take weight off of the float. I know that it is not leaking. Thanks for the tip. I would think that there would be a supplier that would build a float out of the synthetic material that later model automotive applications. They at times would get saturated and cause problems that way, but they were super buoyant. Seems that would be a good fix.

 

[Forward slash]

I might of missed this , but did you test float ? Could it have a hole in it ,full of gas inside float ,will sink when hits fuel .
Put it cold ,get cold , then put submerge in hot warm water and look for air bubbles .

adjustable tang s in float support ,do air low pressure flow test in (like 5 gallon bucket of water) when you get the float adjustment,
i sometimes summerge it in water ,do when this Happen . If it leaks then get back to us. Or talk to carb shop that handles parts. Like YT , mikes carb, McDonald’s in Georgia.

I got a flat surface needle from McDonald Carbs in Georgia for the Farmall Carter Carburetor, been ten years now , talk to them . Might have same for your carburetor ?
Call us back when you find something , helps us

Thanks for the reply. I'm sure the float isn't leaking. I'll be cleaning it's exterior just in case I can get some weight off of it. Wish they would supply one out of synthetic material such as in the old Rochesters I used to rebuild on GM cars. I'll let you know if I get something to work. Thanks again.

 

[Forward slash]

Try setting the float gap at 5/16 inch instead of 1/4 inch like the specs say. I've been doing that on the MS carbs lately to stop the fuel dripping and has always worked so far on the MF tractors.

I've already adjusted the float level as you've suggested. Thanks for the reply. I'll let you know if I come up with something.

 

[Forward slash]

Hello Forward, welcome to YT! Here is a check that can assure you the needle is seating and all is sealing properly. This is best done when the carb has not been put in service yet due to it can be flavorful. Some brake clean and compressed air should get it back to tolerable. What you will do is invert the carb top with the needle and seat installed and the float. With the weight of the float closing the float valve suck on the fuel inlet of the carb then place your tongue on the fitting to capture the vacuum. It should hold the vacuum against your tongue if it is sealing properly.
I would recommend placing all future queries on your N Ford on the 9N, 2N & 8N forum in the manufactures section.

Thanks for the suggestion. Plumbing shouldn't be so difficult. Just glad these old guys are put together with as few fasteners as they are. Nothing like pulling apart the last few generation of carburetors on automobiles.

 

[used red MN]

I'm going to be grinding down the old needle to remove weight from it. Just an experiment.

So your idea is that the float and needle are to heavy and the float is sinking to low in the fuel and raising the fuel level? This is down the lines of the thinking from the early synthetic floats that saturated and got heavy as your referred to in your #6 reply to Tgrasher? I doubt your hypothesis will prove out, there were thousands of machines built and operated thousands of hours with no problem like this. Did some have a drip every couple of hours, maybe. But if they leaked a pint, quart or gallon overnight the carb could be repaired and the leaking stopped. The only way that making the float lighter could fix your problem would be if you have an oddball float with huge globs of solder on it. I have seen plenty of Rochester carbs with brass floats that worked just fine.

 

[wore out]

Thanks for the reply. I'm sure the float isn't leaking. I'll be cleaning it's exterior just in case I can get some weight off of it. Wish they would supply one out of synthetic material such as in the old Rochesters I used to rebuild on GM cars. I'll let you know if I get something to work. Thanks again.

Have you replaced the float?

As someone else said, hundreds of thousands of these carburetors were made (for many other tractors and machines, as well) and did their job flawlessly for many, many years.

You do not need to "re-invent the wheel" here, get to the bottom of what's wrong and fix it, you don't need to make custom parts to accomplish this.

Think of the force available from the float doing it's thing (floating) and the mechanical advantage of nearly all that force being concentrated very near the pivot point, acting on the needle. Once you accept this the TINY amount of weight you could remove from the needle becomes VERY insignificant vs. the available force.

 

[soaked]

Is the needle tip to seat leaking, or is the seat's gasket leaking, or is there a crack or flaw in the casting?
Rig up a test, maybe like this--- so can put eyes on the leak.
Put some gas in the tube, or hose, and watch the seat closely. Expect to need paper towel to see wicking if leak is slow.

If the cast seat 3/8-27NS threads are rusty, the seat may be hard to turn, and feel seated, but not crushing/sealing at the gasket.

 

[SidS]

I fought a ms carb years ago that the owner said had always leaked. He had it repaired several time over the years but could not get it fixed. Like soaked says turn over so you can see and be patient. Find exactly where your leak is. The one I had I finally found the seat bore not square with gasket surface,

 

[M-MAN]

Any wear at all on the float tang where the needle contacts will cause this. I went through three new needle and seats this past spring trying to fix the same problem. Sealed perfectly on the bench and a few days later the same problem. I had noticed the little wear on the tang but didn't think anything about it. Finally decided that with the needle and seat working perfect on the bench it had to be the float. It was. My guess is the wear caused it to push the needle sideways into a bind.

 

[504]

0000 steel wool, work it into a V shape and polish the inside of seat. Then polish the three outer sides of the needle. They are oversized and not finished as well as needed. I think all of the needle and seats are built in the same factory and none of the other as smooth as they should be. I have been doing this to new and old ones for years.

 

[Forward slash]

I did just what I said I was going to do by cutting off a bunch of the bulk of the needle with a dremel tool. Gave it a skinny little waist. In addition, I took some steel wool to the float and scrubbed it down to a nice shine. I'd already polished that contact point where the float contacted the needle. It's sitting out there on the bench with a makeshift reservoir of fuel going into it and so far it hasn't leaked. I'm hoping my troubles are over. I've no doubt there are Ns the world over that have operated correctly for years, but this thing had me puzzled. It's going back on the manifold tomorrow as it is. We'll see. Thanks, all.
'

 

[used red MN]

I did just what I said I was going to do by cutting off a bunch of the bulk of the needle with a dremel tool. Gave it a skinny little waist. In addition, I took some steel wool to the float and scrubbed it down to a nice shine. I'd already polished that contact point where the float contacted the needle. It's sitting out there on the bench with a makeshift reservoir of fuel going into it and so far it hasn't leaked. I'm hoping my troubles are over. I've no doubt there are Ns the world over that have operated correctly for years, but this thing had me puzzled. It's going back on the manifold tomorrow as it is. We'll see. Thanks, all.
'

Hope it works out for you. Only thing I could see that might be a problem is a roughly machined
iD of the needle seat causing the needle valve to hang up and stick.

 

[showcrop]

The last 2-3 kits that I got have a spring clip that goes into a groove in the needle and attaches to the float so that the float actually PULLS the needle down, instead of depending on gravity.