your low speed circuit is restricted , spray some carb cleaner into it . Always add fuel cleaner into your fuel routinely !

Thx for reply. i do use sea foam. i ended up buying new carb because i got frustrated with old one. i claened the old one to no avail.

new carb does same thing. it will only run on high. as soon as i release trigger to idle it stalls

Your low speed jet controls off idle performance . Ensure it is set 1-1/4 to 1-1/2 out from gently seated . Another possibility is that you have an air leak . Carb flange loose or gasket cracked , gas line cracked or crank seals worn . Inspect to determine !