Joe,

I meant what I wrote.

In a bushing bearing engine, the crankshaft both spins and seals against the bushing.
Below the carburettor there is a port, which when the port in the crankshaft is in line with, air and fuel are sucked into the crankcase chamber (under the piston). When the two ports are out of alignment very little oil, or pressure leaks out.

A ball bearing engine works essentially the same way, but since the crankcase front housing is not used as a bearing surface, less oil clearance is needed between the two components. The crankshaft should seal against the front housing, when the two ports are out of alignment, so no major leakage should take place.

If it does, the seal is bad, which means either the crankshaft, or the front housing (or both) is worn, or they are mismatched for size.

If the bearing has excessive internal freedom (balls are too loose), the crankshaft will wobble and wear itself and the corresponding, front housing internal surface and quickly enough, you have got a leak of air (intake), or fuel, or both.