All carbed scoots experience stalling, no starts, etc. after storage. You said you drained all fuel and the scoot sat dry for three months. All, but fuel in the carb... when the fuel in the carb dried, all is left is varnish... and varnish when it dries becomes a hard crystal-like coating clogging things in there. If carb clean can't do the job, you have to open it up and clean.