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One thing that can give you trouble like that is trash in the fuel tank itself.. like a big rust flake floating around that floats over/partially blocks the outlet of the tank. However, since you say you have good fuel flow..Then the other thing that I have seen is the main air bleed be clogged partially. The main air bleed is the little copper pipe that sticks up into the venturi. If you pull the needle valve off the bottom of the lower carb bowel, you will see this. The needle valve on the bottom of the carb is what controls the fuel/air mixture at high speed outside of low rpm. Take off the lower needle valve.. then you can unscrew the main air bleed and remove it. Be careful when you are removing it and reinstalling it. Its only brass and does not take alot of torque either way. When you put it back in, just snug it lightly. It should have a gasket on it. Make sure that all of the little air passages in the thing are free of debris. Just 1 of those little holes plugged up can cause your problem. - Ie.. you are getting too much air and not enough fuel.. that is why it runs better when you pull on the choke - runs richer. Clean all this out. Its easy when that needle valve/air bleed are removed to blow out all of the Carb. passages with compressed air. Check your float setting too. Without knowing your carb model, I cannot advise you on this. Most are 1/4 inch from the bowel bottom to the top of the float when it is hanging. As for the needle valves. The default setting of the lower needle valve is 1-1/2 to 2 turns out. The only way to really set it is to have the tractor under load and adjust it. However, that is usually next to impossible for most to do. Just set it at the default setting. The upper needle valve in the upper carb bowl top is set the same. 1-1/2 to 2 turns. Hopefully, just taking it apart, cleaning it again will solve your problem. Phil
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