This from the website:
There is oil leaking from my PRO4?
Check for proper oil level. The PRO4 engine is similar to a 4-Stroke lawnmower engine, which will leak oil if tipped upside-down. Store and transport the unit with the recoil or the spark plug in the up position. This will prevent oil from migrating from the crankcase through the vent hose into the carburetor. Should this accidentally occur, run the engine outdoors, exhaust will smoke until the oil has been cleared from the carburetor.