70 update and 50 carb question

First make sure your float "floats". If it leaks and gets gas inside it then it will sink to the bottom of the chamber and allow gas to flood the engine.

If the float looks good and does not bind on its pivot you should be able to replace the needle and seat and simply make sure the float is "set" properly. I believe the float should be set so that the needle is closed when the float is even with the carb seam. The float is adjusted by bending the tab which contacts the needle valve. I usually blow into the gas inlet and move the float up to make sure the needle is seating properly.

The parts found in carb kits vary somewhat. Often there will be a new throttle shaft and bushings. If your throttle shaft is worn it will likely leak air and cause uneven running. If you choose to replace the throttle shaft and bushings you may need to ream the new bushings to fit the shaft. Make sure the throttle moves freely.

Also make sure the choke is operating properly. Sometimes that little spring breaks and the butterfly plates won't open.

Best of luck,
John