10 lbs. pressure might be a touch high. 5 lbs. should tell the story and is less likely to blow out seals and gaskets. You really need to put the pressure to it with a hand pump; it is way too easy with compressed air from a compressor to instantly get way too much pressure.

Sometimes you can spray WD-40 or carb cleaner spray around the shaft seals, the crankcase parting line, the reed valve gasket surfaces and the carb to manifold surfaces, etc. and see if the engine changes tune or speed. That will tell you there is a leak. The "intake tract" is just the carb, manifold, reed valve, and any adapters in between. Be very careful of that spinning prop while doing this!

AV8TOR