I regularly work on small engines of all sizes from weed eaters, lawn tractors, motorcycles, up through auto engines. Here is what I have discovered and it may be a solution to your idling problem. The small fuel galleries supplying fuel to the jet are very prone to varnishing closed because of their small size. It doesn't take long for varnish to form in a machine that is idle - especially in a seasonal or seldom used engine. When this happens the idle jetting is the first to foul and if you have any question try this. The engine will likely run only with the choke pulled because it needs a richer mixture. This is proof that the fuel is insufficient without the choke on. Choking the engine restricts air flow thus balancing the air/fuel mixture to allow the motor to run. To fix this I never remove the carb, but rather use healthy doses of Stabil gas additive to the fuel at about 6 oz per gallon and run that through the engine. That dosage can be reduced as the process proceeds. How many tanks will it take to get back normal fuel flow depends on how plugged the gallery is. Just continue to run with the choke on to keep the fuel flowing and the more you run it the quicker it will clean out. I also use Lucas Upper Cylinder additive to help this process. Some folks prefer Marvel Mystery oil and Seafoam in the fuel, and I guess that works okay too, but I haven't used it enough to have the same confidence in it as I do in Stabil. Proof that the carb is getting cleaned is when you can open the throttle more and need less choke. The ideal is to be able to open the throttle quickly and not have the engine cough or hesitate. I'm pretty positive that if you do this you will clean out the carb. Now, once you have that done, do your prevention and always add whatever brand additive you like to the fuel and for this I prefer the Lucas product. That cleans the carb and also helps unstick the compression rings. People who live in a hot climate run into this type fuel related problem because of the faster evaporation of the fuel. And no, don't blame it on old gas....i've run engines on 2 yo old gas with no problem. I take motors that won't run and "fix" them easily with this method if it's a fuel problem.