Any crankcase induction 2 stroke (in other words, almost all cheap 2 strokes) sucks mixture into the crankcase when the piston is moving up to the top of the cylinder (called the crankcase induction process), then compresses that mixture in the crankcase when the piston moves down the cylinder (called the crankcase compression process). Towards the end of the piston's down-stroke, the transfer port opens allowing the compressed mixture to flow from the crankcase into the cylinder. So, there is crankcase compression when the piston moves downward as well as cylinder compression when the piston moves upward. That means you can feel two compressions per revolution of the engine. Leaky crankcase seals allow mixture to escape during crankcase compression, and also allow pure air (with no fuel in it) to enter the crankcase during crankcase induction. So, leaky crankcase seals means the engine will run badly if at all.
If your top crankshaft seal has blown out once, it may do so again, so your problem may come back.
