Your getting it to start and run by hand choking is indicative of weak spark (weak sparks need richer mixtures),inadequate fuel delivery( float setting or fuel delivery blockage) resulting in a lean mixture, a vacuum leak around the carbs metering section, a maladjusted carb or a dirty carb.
If you have a good spark(FAT AND BLUISH-WHITE, the color of lightning), then checkthe fuel delivery to the carb. Hold a can under the carb and remove the plug from the carb"s fuel bowl.You should have a CONTINUOUS gush of fuel from the bottom of the carb. If it dribbles or is intermittentent, you need to check the flters in the sedimentbowl/tank valve and the fuel inlet elbow to the carb. If you have adeqate fuel delivery, check the carb mixture adjustments(1-1/4 turns out on the power jet and 3/4 turns out on the idle air). You can check for air leaks( carb shaft seals, carb to manifold gasket, manifold to cylinder head gasket, cracked or rusted) using starting fluid sprayed around these locations with the engine running. When you hit the leak, the engine will speed up momentarily. If that checks out, your carb probably needs a good cleaning esepcially in the area of the idle and transition fuel passages.