over priming leaks are likely poor carb float shut off problems which basicaly work just like toilet bowls. When full no more water flows in “reservoir” same thing with carbs !
Some leaking when tilted up may simply leaking out the carb’s open air vent used for atmospheric balance. As the carb fuel gets sucked in the engine the vent prevents vacum build up in the carb. This “vent” concept may or may not apply to pressure tank systems but check anyway where exactly the leak originates.
In any event openning the tank cap will drop the built-up pressure on the fuel distribution.
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