On all model engines, you must have some oil come through the front bearing. This is how it gets lubricated. The engine should not spray raw fuel from the front bearing when it's running. If the engine sprays fuel through the front bearing, it's not signs of a bad bearing, but of too much clearance between the crankshaft and the crankcase immediately behind the bearing.

The front seal is made by a thin film of oil between the crankshaft and the crankcase. The bearing has very little to do with the seal. In fact, under normal circumstances, it's virtually impossible for a model engine to suck air into the case through the front bearing. The dynamics are such that fuel is forced out through the bearing, not air in.

If an engine has good compression, a good plug, and good fuel, it WILL run. You just have to get the mixture correct. It's very common for engines to be over or under-primed, and either condition will prevent it from starting.