Oil level check

 Watch this video!

https://www.rotax-owner.com/en/videos-topmenu/expanded-video-instructions/36-exp-si-27-1997

Actually it is the opposite...

An engine with a tight seal by the rings "leaks" only a little bit and therefore needs more turns to pump the oil back to the tank. An older engine easier to do. FYI my compressions are (80,80,80,79).

Well.. that sort of depends on where/how the pressure is being lost.  I have similar compression numbers to yours on a 300h engine and it NEVER takes me anything near 30 strokes to get the burp (nor has it ever).  Puzzling.

If you watch the video in the third post up,  The operator is cranking way too fast.

He is pulling the prop right through the compression peaks.

When you hit a compression point, STOP, count to 2 and then move the prop tip another 2 inches and STOP.

Keep repeating the move and Stop routine until you stop feeing compression and then feel free to move quickly to the next compression point.

There are 5 compressions per prop revolution. One every 74° to be exact.

The object is NOT to crank the prop through a lot of compressions.

The object is to crank Slooowly through Each compression point to get the Most bypass gas that you can.

It does not help to rush the process.

Even with a lot of Oil in the sump, 3 rotation, 15 compressions should produce the "Burp".

. . .

Like Glenn said, "Take it as Rotax Zen", it is Not supposed to be an "... Upper Body Work Out!" 

. . .

Even if there is No Oil to return, you will always get a "Burp".

The IN fitting on the Oil tank terminates a few inches below the Oil level in the tank.

The byass gas will always bubble up through the Oil and produce the distinctive sound.

It is possible that you have way more oil in the sump than you expect and more cranking is needed.

Once you hear the Burp, wait a few seconds and another few compressions will produce another one even though you already know the sump is dry.

And its easy to practice Rotax Zen!  When you eventually get the oil to burp, continue slowly pulling the prop through additional individual compression events and listen / feel the burps -- be one with the burps -- Ohhhmmmmm........