Choke on

Sounds like your idle jet is clogged. This is caused by gasoline evaporating out of the carburator during long periods of disuse which can leave a varnish residue. You will probably need to remove the float bowl and remove the jet to clear it as carb cleaning additives in the gasoline are usually useless for this problem. It is vital that you use the exact fit screw driver on float bowl screws as they are usually very tight. The jet will have a very small opening and you could damage the jet if you use the wrong method to clean it (do not use a drill bit). First try a carburator cleaner spray with the small plastic straw that comes with them. Look thru the jet hole by holding it up to a strong light to see that it is indeed clogged. Then try holding the small straw in the jet orifice and forcing the cleaner into and through the jet. Be careful that you don't deflect the spray back into your eyes. Use eye protection. You could try to soak the jet in a cap full off the cleaner for a while. If that doesn't work a very small stiff wire might work to push the clog out (from a wire brush?). Then try the spray method again.