Does it have an idle mixture adjustment? I know there's an idle speed adjustment screw but some carbs have another screw that's for the idle mixture, it could be set too rich or too lean, but typically start out by turning it in until it Softly bottoms out, then back it out 1 1/2 or 2 turns. This should let it idle, then adjust it in until it stumbles the engine, now back it out counting the turns until it stumbles on the rich side. Now go back in half the number of turns you went out, that's where the engine should idle at its best.
If your carb don't have an idle mixture screw, check for any air leaks where the carb connects to the intake, and at the intake where it connects to the head. If the engine runs but you have to constantly blip the throttle to keep it running it's usually going to be a mixture related issue where you're either getting too much fuel or not enough either due to vacuum leaks or improper idle mixture adjustment. It could also be due to something blocking the fuel passages inside the carb where you will need to remove the carb and take the float bowl off, then you can clean it with carb and choke spray and a set of welding tip cleaners to dislodge any tiny debris that may be in the tiny fuel passages inside the carb.