RE: OS52FS Idle Adjust
There is no airbleed hole. The carburetor for your engine does not use an airbleed hole for idle mixture adjustment. There is a small screw next to the needle valve where you adjust the idle mixture. The air enters the carburetor through the venturi. On the exploded diagram of the carburetor, part #4, nozzle assembly, has the idle mixture adjustment.
If the engine won't transition from low to high, you'll need to check the entire fuel system to make sure it's OK, and then get the engine properly set. If a fuel passage has gotten something into it, then you'll have to clean the carb.