Re: almost closed petcock gives me more power
again take the carb off the motor then take the manifold off the jug and inspect the manifold for casting flash, welding slag and blockages clean them up.
take the bottom of your carb off and remove the float and float pin needle, it sounds to me your float bowl is adjusted too high or stuck open causing flooding and bogging. bend the tab ever so slightly that hold the float pin so that it sits lower in the bowl.
this will alow the carb to shut the fuel off before it fkloods and bogs out.
before putting the carb back together spray every channel out with carb cleaner
change your spark plug and get it all back to gether and let us know how things go.