Just sitting around for a long time doesn't effect gas engines like it does glow engines. If it's running but not running well it is usually just not in tune. Either timing or the carb needles. I just fired up one of mine that was in a crash then put under the bench several years ago. I did have to set the timing after I installed a new ignition but it fired right up. It then required the needles to be re-set. I had to replace one of the needles due to a bit of a bend so I knew it had to be adjusted a little. I have a mag on my Zinoah G-62 and that engine sits under the bench for a decade or more and usually fires right up when needed. I have rebuilt the carb on this engine once when the diaphragm stiffened up. You can get a complete carb kit from any small engine repair shop if you think you need one. I do like Jester said and just use a spray can of cleaner to flush them out. If you stored the engine wet after running then the diaphragm may be a bit stiff but it does sound like it just needs to be tweaked on a little bit.