Fuel bowl restricts gas on 9n

I have a 9n that runs fine at low rpm but coughs and sputters at higher rpm/power. The roughnerss at higher rpm smooths out of I pull the choke about halfway or so, then goes back to rough (too lean) when I let go of the choke knob. The old fuel bowl valve was missing the screen on top and clogged so I replaced it. Now I have the problem where if I tighten the bowl up to where the gasket seals and there is no leak, no fuel flows at all from the tank when I open the valve two turns (or more). I did this with a dry fuel bowl so I could see what was going on. If I loosen the bowl to where fuel flows down freely, its so loose it leaks at the seal and runs down on the engine block.

I have both a new carb and the original rebuilt marvel shebler, same with both, so I don?t suspect its the carb. Fuel line (copper) and brass are all in good shape. Any ideas?

Not your problem. Normal not to fill the glass bowl. Drain some gas from the bottom of the carb and glass bowl will fill.

You have carburetor problems if necessary to choke to get it to run!

Check with a flashlight in your gas tank to look for obstructions or crud buildup. This happened to me on an M Farmall. Ellis

More likely restricted fuel flow from the tank than carb problems. Pulling out the choke restricts the air flow so it then balances out with the available fuel. Drain the gas tank, unscrew the sediment bulb fixture, and put in a 1" long "stand pipe" made from the appropriate size copper tubing, so it draws fuel from an inch above the sediment in the bottom.

I wrapped a rag around my air compressor blow nozzle and blew the gunk thru the drain (with glass bowl off) into a bucket. Cleared it out. You could also pull the tank + valve and flush the tank thru the valve hole. The crud will haunt you at the worst times until you get it all out.

(quoted from post at 10:53:41 04/14/19) Not your problem. Normal not to fill the glass bowl. Drain some gas from the bottom of the carb and glass bowl will fill.

You have carburetor problems if necessary to choke to get it to run!

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Roger has it correct.

If carb is full, no fuel will flow and sediment bowl won't fill until the carb float drops and allows gas to flow.

If it runs better with choke, that indicates a carb problem.

If fuel flow to carb REALLY was restricted, it would run better for a few seconds as it sucked the float bowl empty, then stall.

Clean your carb.

Don't worry about air in the bowl. It will come out when there is a fuel demand.

Weak spark can also cause the symptoms you describe. Check for a blue hot spark at each plug. Each wire should be making at least a 1/4" spark to ground at the plug end of the wire. Check the point gap and condition.

To check fuel availability to the carb, with the engine off, fuel valve open to normal run position, and plenty of fuel in the tank, get a clean glass container, remove the drain plug from the carb bowl, and catch the flow in the glass. It should have a full flow at first, then slow as the bowl empties, but it should still flow a stream, not slow to a drip or stop flowing.

Look at what was caught, if it's cloudy, that's water. If chunks of rust or dirt, it needs to come off and be rinsed out. Whatever is in the glass will also be in the carb. Once the tank is clean, the carb may need to be opened up and cleaned out. That can usually be done without a kit if careful with the gasket.

If there is little flow through the carb, start checking back to the tank for a restriction. There may be a screen in the fuel fitting at the carb.

Once the spark is right, the fuel is supplied and clean, the carb is clean, air cleaner serviced (including the wire mesh), it may be necessary to set the high speed jet.

To do so, get the engine up to operating temp, adjust the idle speed down to 400-500 RPM. Adjust the idle mixture screw (the small screw up top) for the best idle, then slightly rich.

Then adjust the main jet screw. To do so, idle the engine down, then suddenly open the throttle, listen for the response. If it hesitates, back the main screw out 1/2 turn, repeat the test. Keep repeating until the engine will take sudden throttle without hesitation. Continuous black smoke indicates too rich, turn it in some. The final goal is to have instant throttle response without hesitation, and just a single puff of black smoke.

Is your gas cap allowing air to enter the gas tank so that things aren't air locked?

Thanks everyone for the responses, I forgot to mention that I have no air cleaner present, it didn?t have one when I bought the tractor, but the tractor ran fine when I bought it.

More than likely the previous owner tossed the air cleaner because the motor has low compression. A lot of times the gasket between the carb and manifold will go bad or the gasket between the manifold and block will goad. When this happens you will have to pull the choke to get it to run. You need to check the compression.