40 B carb troubles

Farmallb

Well-known Member
Carb SLOWLY loads up. when it is full it drips or runs out on the ground depending on how much I have the gas turned on at the bowl,. When started, it will blow black smoke for a minute or two, then clear out and run for say 5 minutes or so then shut down. Wait for an hour for the bowl to fill and do it again.
Ive had it to a mechanic 4 times, and hes been out here 2 times for both the B and my 48 H carb troubles. Im losing faith in him by now. He takes the B carb, and I pick it up the next day, and its no better. As to the H, He says he can fill the hole, then tap it out, and make a screw for the idle adjustment. Im trying to find which is cheaper, him doing that, or me finding another top for the H carb.
Hes also got my 50 Cub carb. I havnt heard anything about it. Ive paid $50 so far on the H carb minus the kit, and $30 on the B minus the kit.
 
If you have gas dripping out of the carburetor, it sounds like the needle valve is not sealing when it is closed, or the float is not adjusted properly. The float is what closes the needle valve.

Take off the gas line at the carb. Get a can and turn on the gas at the tank. It should run into the can freely. If not, you have blockage in either the sediment bowl or the fuel line. The needle valve has to stop that flow when the carburetor is full, if it doesn't, the carburetor will run over and spill gas on the ground. An over full carburetor will run rich and cause the black smoke when it starts. A partially blocked fuel line could cause the engine to shut down after it runs for 5 minutes or so.

I would have the carburetor gone over by somebody who is better with carburetors.
 
I agree with Red Dave. There is a screen in the fitting where it attaches to the carb, and a screen in the sediment bowl. no other filter should be in the supply. These need to be clean. The connection from the sediment bowl to the tank can get trash in it, preventing full flow. The fuel should flow from the carb supply fitting to fill a pint jar in 2 minutes or less. If not the lines or sediment bowl is partially plugged up. Leaking needle and seat (or seat to carb top) are the cause of the flooding when stopped. Find a better qualified carb service. Denny's Carb shop is not a recommended place!!! Jim
 
(quoted from post at 19:15:21 11/14/17) Carb SLOWLY loads up. when it is full it drips or runs out on the ground depending on how much I have the gas turned on at the bowl,. . . .
Fiddling with the shutoff under the tank is not a way to deal with an overflowing carburetor. The shutoff valve should be either fully open or fully closed. Never leave it anywhere between. If you can't totally eliminate carb overflow be fixing the carb, you will have to close the shutoff valve whenever you aren't running it.
 
(quoted from post at 17:15:21 11/14/17) Carb SLOWLY loads up. when it is full it drips or runs out on the ground depending on how much I have the gas turned on at the bowl,. When started, it will blow black smoke for a minute or two, then clear out and run for say 5 minutes or so then shut down. Wait for an hour for the bowl to fill and do it again.
Ive had it to a mechanic 4 times, and hes been out here 2 times for both the B and my 48 H carb troubles. Im losing faith in him by now. He takes the B carb, and I pick it up the next day, and its no better. As to the H, He says he can fill the hole, then tap it out, and make a screw for the idle adjustment. Im trying to find which is cheaper, him doing that, or me finding another top for the H carb.
Hes also got my 50 Cub carb. I havnt heard anything about it. Ive paid $50 so far on the H carb minus the kit, and $30 on the B minus the kit.

You need to find a mechanic who is old enough to have a working knowledge of carburetors. If his only experience is with diesels, or electronic fuel injection, he won't do you much good on a 70 year old carburetor.
 
the mechanic is in his 50s.
I always shut off the fuel line at the bowl and let the tractor run out whats in the carb
How do I know if the bowl is properly vented?
O took the fuel line off and ran a gal of gas out of it to see if there were any stoppages. There wernt.
I put a in line fuel filter on the gas line. Didn't help. The tank is now empty enough that the tractor wont start. Im going to put a can of kreem in the tank to seel whats in it.
Nobody round here has a sign out saying there expert with 70yr old carbs.
 
Judging by the symptoms you describe, it is also possible that your float/needle valve is not operating freely. It may be binding or rubbing on something inside the carb after it is assembled.

Your description sounds like the needle valve is not allowing full flow of gas into the carburetor and also not closing it off completely when the carb is full.

If you can't get it solved, new replacement carburetors are available from several aftermarket parts suppliers, including this site (link below). I have not yet needed to try one, so I have no first hand experience with the replacements. They are not cheap.
YT Magazine after market carburetors for Farmall B
 
(quoted from post at 09:41:54 11/15/17) the mechanic is in his 50s.
I always shut off the fuel line at the bowl and let the tractor run out whats in the carb
How do I know if the bowl is properly vented?
O took the fuel line off and ran a gal of gas out of it to see if there were any stoppages. There wernt.
I put a in line fuel filter on the gas line. Didn't help. The tank is now empty enough that the tractor wont start. Im going to put a can of kreem in the tank to seel whats in it.
Nobody round here has a sign out saying there expert with 70yr old carbs.

No. Most of the guys who would be considered "expert" are either retired, or have passed on. Is there a tractor club in your area? You just might find a retired expert who will help you.
 

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