how can I fix my spear and jackson hedge trimmer spjht 26?

I left fuel in machine over winter , it start's but wont continue to run , have  drained fuel out and put new in ,same problem ,have cleaned plug and air filter still no good ,took carb off and stripped checked jet's etc put back ,start's as before and then stop's , it was working alright for three year's only had to clean plug and air filter , any suggestion .