I know I have posted this before; but, it is possible (especially since you haven't driven it much this year) for the fuel to schalaque (sp? anyway go bad) and cause things (like a valve or a carb) to gum up. Usually there are other signs of this or a sticking valve too though. Like backfiring through carb/exhaust, very low power etc.

Anyway, if the valve is sticking in the guide and causing this, one thing you can try is this:

Start the vehicle, and get it idleing. Remove the air cleaner and raise the throttle a bit off of idle. Next SLOWLY pour a small amount (about a tablespoon) of automatic tranny fluid into the carb. DONT let the motor die while you are doing this or it will fowl the plugs. As the tranny fluid burns in the cylinder along with the A/F mixture it will lubricate the valves and should free up any that are sticking on you.

Good Luck,
Firechicken