On all small gas fueled engines that are infrequently used, it is important to drain the carb after use. All small Hondas (including the bikes) have a drain valve at the bottom of the carb bowl just for this purpose. Running the motor until it quits still leaves residue in the carb. The left over fuel turns to gunk then varnish, blocking jets and other orifices resulting in hard staring and poor performance. If this is too late and it's already running bad, try some SeaFoam (or other) additive. If you're lucky, it will clean things up and save a carb overhaul.
Norm