I agree with the compression tester, I bought one for ~$35 at the local auto parts store...you could potentially spend more than that in gaskets if you start taking apart the engine, let alone all those little tools that your never knew you needed.
EXACTLY when does it puke the oil? Within a few seconds of starting, just idling, only when you rev it, after a few mins or imediately...ect.? The devil is in the details, the more detailed you give the easier it is for someone to help. AFAWK the only possible way for oil to come out the vent tube is if there is excess liquid in the crank case. How clear is your sight glass, can you clearly see the exact oil level?

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