Given the effect the choke has, you know for certain that this is a fuel delivery issue. For the first two years I owned my 350 Utility I had this problem almost daily. I finally got off my lazy butt and solved the problem once and for all. My problem was a rusted gas tank. Etched it and lined it with Kreem and the problem went away for good. Now, to your diagnosis. Somewhere between your gas cap and your intake manifold you have an obstruction in your fuel delivery. To diagnose this, start the tractor, run it in neutral until is stalls from fuel starvation. Immediately pull the drain plug out of the bottom of your carb bowl. If you do this quickly, you will find the bowl empty or almost empty. Fuel may even be dripping out, but slowly. If you get a fast and full stream coming out the drain plug for more than a few second, then your problem is downstream of the float-valve.
Upstream Problems (those between the bowl and the gas cap) - my most common locations for restriction were the fuel strainer where the fuel line enters the carb and the gas line itself. To clear the fuel line I blew compressed air back into the gas tank through the gas line with the gas cap removed (Otherwise you pressurize the gas tank and can get a big flood of gas in your lap). The strainer is the located inside the carb but attached to the fitting that the fuel line attaches to. I am trying to think of a better way to describe this but I will do my best. The fitting where the fuel line attaches to the carb is actualy dual purpose. The outward end of it is the seat for the fuel line. The inward side of it is a very fine cylindrical screen that acts as a fuel filter. I often had to pull this fitting out of the carb and the clean it out with compressed air.
You should also have a good look at your sediment bowl filter - is it plugged? What about the gas cap - right after is stalls, if you crack the gas cap do you hear it sucking in air? If so, try running with gas cap off, if it doesn't stall, you have found your problem. Replace the cap.
Downstream Problems - If you find that you have good unobstructed fuel delivery from the gas cap to the carb bowl, then your problem is between the Carb bowl and the intake manifold. I found lots of plugged passages and fouled jets due to crud getting past the filters. A $20 carb rebuild kit from NAPA and an afternoon with pipe cleaners, acetate, compressed air and a lot of patience, resulted in a well functioning rebuilt carb.If this is too much detail about diagnosing your fuel delivery issue, just go on to the next post. If you want more detail, just reply back to this post and I will help out more where I can. Good luck,
Sean in Calgary.
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