2N carb question

On the carborator on my 2N, what is the "Air horn plug" on the bottom of the fuel bowl for? Its a small plug directly to the front of the drain plug with a small hole in it. It leaks gas after I turn off the engine, however when the engine is running, it does not. Could air be getting sucked in through the hole in this plug?

It is supposed to drain excess gas in the bowl.

There should be a "horsehair" (older carb) or sintered bronze "filter" (newer carb) in there to let overflowed gas OUT, and prevent the entry of ambient dirt.

The "filter" is still available, if your's is missing.

hunting.......the "air horn plug" is supposed to be plugged with either a "felt" filter ...or... "sinstered" bronze-balls filter. The filter is very fine to keep DIRT from entering the carb, yet allow overflowing gasoline to drain out.

Why does the carb overflow? Could be from excessive cranking and "flooding" the stalled engine ...or... yer carb float valve not sealing and allowing the constant gravity flow to overflow the carb bowl and drain out the carb mouth.

ALWAYS remember to completely TURN OFF the under the tank valve when yer done tractoring for the day. This prevents "flooding". ......Dell

Dell...When my tractor is running, there is no leakage of fuel out of that hole in the air horn plug. However, when I turn my tractor off, whatever fuel is in that bowl seems to leak out after I close the shut off valve on the sediment bowl. Now, when my tractor is running, it will run smooth for a bit, then it will begin to die off, like its either being starved of gas or getting too much gas. If I pull the choke out for a split second, or if I vary the position of the throttle, it will sputter itself back to running smooth for a bit again. That is why I was thinking air may be getting sucked in through that hole. I also noticed that air bubbles are getting sucked into teh sediment bowl when the tractor is running. Obviously I need a new seal there. I rebuilt the carb, including a new carb float valve. This is my first "toy tractor", so I'm learning as I go. Thanks for your feedback and any other help anyone can give.

(quoted from post at 09:53:29 11/04/08) Dell...When my tractor is running, there is no leakage of fuel out of that hole in the air horn plug. However, when I turn my tractor off, whatever fuel is in that bowl seems to leak out after I close the shut off valve on the sediment bowl. Now, when my tractor is running, it will run smooth for a bit, then it will begin to die off, like its either being starved of gas or getting too much gas. If I pull the choke out for a split second, or if I vary the position of the throttle, it will sputter itself back to running smooth for a bit again. That is why I was thinking air may be getting sucked in through that hole. I also noticed that air bubbles are getting sucked into teh sediment bowl when the tractor is running. Obviously I need a new seal there. I rebuilt the carb, including a new carb float valve. This is my first "toy tractor", so I'm learning as I go. Thanks for your feedback and any other help anyone can give.

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"also noticed that air bubbles are getting sucked into teh sediment bowl when the tractor is running. "

Well, unless you have blockage in the tank vent, tank/valve ahead of sediment bowl this "sucking air into" affair can not occur. The fuel level being above (higher elevation) than the bowl, means the bowl has a higher pressure on it than the atmosphere. Therefore any leak at that point would necessarily be fuel OUT, not air IN.

JMOR... Thanks for the input. When I had the tractor running on Sunday, I noticed when looking into the sediment bowl that small bubbles were appearing at the top, as if they were getting sucked in. I have had the entire sediment bowl assembly off and cleaned it, however there was not much dirt there. I guess I'm not sure where the tank vent is to check if that is clogged. I'll have to check my shop manual. Could my tractor be starving for fuel when its running that it is trying to suck fuel faster through the gas line/sediment bowl? This could explain why it runs rough at times, that is until I open up the throttle or pull the choke out for a split second. Or is fuel strickly gravity fed into the carb? What would happen if I open the main needle valve way open...currently its at about 2 full turns from seated. Sorry for all the questions.

(quoted from post at 14:23:22 11/04/08) JMOR... Thanks for the input. When I had the tractor running on Sunday, I noticed when looking into the sediment bowl that small bubbles were appearing at the top, as if they were getting sucked in. I have had the entire sediment bowl assembly off and cleaned it, however there was not much dirt there. I guess I'm not sure where the tank vent is to check if that is clogged. I'll have to check my shop manual. Could my tractor be starving for fuel when its running that it is trying to suck fuel faster through the gas line/sediment bowl? This could explain why it runs rough at times, that is until I open up the throttle or pull the choke out for a split second. Or is fuel strickly gravity fed into the carb? What would happen if I open the main needle valve way open...currently its at about 2 full turns from seated. Sorry for all the questions.

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JMOR... Thanks for the input. When I had the tractor running on Sunday, I noticed when looking into the sediment bowl that small bubbles were appearing at the top, as if they were getting sucked in. I have had the entire sediment bowl assembly off and cleaned it, however there was not much dirt there. I guess I'm not sure where the tank vent is to check if that is clogged. I'll have to check my shop manual.
ANSWER: Hard to check that vent due to location and design, but simply loosening the gas tank cap will produce a 'for sure' temporary vent. Listen for sucking air sound as you open it and if open while running, does it make an improvement?
Could my tractor be starving for fuel when its running that it is trying to suck fuel faster through the gas line/sediment bowl? This could explain why it runs rough at times, that is until I open up the throttle or pull the choke out for a split second. Or is fuel strickly gravity fed into the carb?
ANSWER: If it needs more fuel that it can get thru sediment bowl/line, then it means something along the flow path is clogged or the vent clogged.
What would happen if I open the main needle valve way open...currently its at about 2 full turns from seated.
ANSWER: Probably enrich the air/fuel mixture. "Probably", is because you could already be at maximum rich condition. In these carbs that Main Power Adjust needle is directly in series with the MAIN JET, therefore, which ever of the two is the smaller opening, determines the mixture.
Sorry for all the questions.
COMMENT: If choking improves condition, that generally means it was too lean and the choke richened it a bit. Sometimes this can mask a weak ignition. With fuel running out bottom of carb, it is more likely too rich. Does it produce a sooty black smoke (too rich)? The needle/float assembly is supposed to shut off the flow into the carb when the fuel level is about 1/4 inch below the top/bottom carb split gasket. If this is as it should be, then fuel should not be running out bottom of carb , with the exception of excessive choke application at start up.
Needle seat assembly: The seat may not be sealing properly to carb body due to gasket or simply not tight enough. The needle to seat seal may not be good or have a tiny piece of trash in it.
MYSELF: I would try to stop the 'fuel leaking out of bottom of carb' before worrying about how it runs. Fix that & it will like start to run just fine.