Have a late 60's deere 112 with a 10hp tecumseh HH100 in it. Worked fine last week, this week not. Fill up tank and gas spews out main jet of carb.

Things I've done:
*Tested float - it floats, no leaks
*Cleaned needle and seat
*Dropped bowl down about 1/8" so I could see what happens with float when gas fills up bowl. Guess what.. it stops the gas. Seat the bowl on gasket, gas starts flowing. This one really baffles me.
*Cleaned out carb good to no avail.
*I even cut the bottom out of a pop can and set in place of the bowl so I could really see what happens when the bottom of the can filled up against the float. Float worked as normal, pushed the needle up and stopped the gas. I have a rebuild kit on the way but not sure this is going to solve the problem.

Any ideas????? First post, thanks in advance for the help.

Chagne the needle and seat, that is what is worng, take the bowl off, lift the float to the close position with you finger lightly, hold it for 2-3 seconds and release it slowly you will probably hear a slight ping and the it will fall to the open position, they are not expensive, if you have an old briggs points plunger the are perfect to push the new one in, the ruber rings on the seat go up, good luck, Light Mechanic

Make sure the float vent is open and not plugged, little hole on the side of the carburetor above the low speed adjustment screw, opens up into the area above the welch plug inside the carburetor. If the vent is plugged, atmospheric pressure can hold float down and allow fuel to flow. If the vent is clear then I would try a new needle and seat as lightmechanic suggested, and if it still leaks, then a new float. I have had issues with floats that seemed alright but just would not seat the needle.

Thanks for the help. I will be following both of your recommendations. Much appreciated.