How long between starts needs prop oil burping?

... hmmm, not sure if this thread still has a heartbeat, but the OP asked a ? about any evidence for damage w/o burping.  A pal of mine ran a UL rotax for well over 1000 hrs and never burped it.  I note the oil tank is apparently not sealed by the tank cap, (as it can overflow excess oil) so i ask, can you 'burp" the tank w/ the cap on (obviously you wont hear it) ?  My plane makes it a pain to access & it doesnt burn but a 100 ml of sport 4 per 25 hrs!, so I'd like to just spin the prop w/ the starter w/ the mags off to burp it.  I only check the oil when i have a passenger &-or ~ every 10 hrs.  Pity rotax doesnt use a sight glass to observe the oil & coolant levels.

When i do the full oil check cold, i notice my oil dipstick is lowered after burping (?) as much as 20% of the flat area (~ .5 ltr), I'd have thought it should rise ?

Not sure what the advantage would be with  "Burping" with the cap ON. ???

If you listen closely you can still hear the burp, but probably not if you are out on the ramp.

You will still need to remove the cap to check the Oil level.

The only reason for Burping is to return all the Oil to the tank for a level check.

If you do not intend on checking the Oil Level, there is no need to Burp the engine in the first place.

John Wrote:

...  I'd like to just spin the prop w/ the starter w/ the mags off to burp it. ... When I do the full oil check cold, I notice my oil dipstick is lowered after burping (?) as much as 20% of the flat area (~ .5 ltr), I'd have thought it should rise?

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If you spin the prop with the starter, you are pumping more Oil than you are returning.

Without the cylinders firing, there is very little bypass gas to return Oil.

To Burp, you need to turn the prop Slowly by Hand and pause at the top of each compression stroke to allow for sufficient time for the compressed gas to leak into the crankcase.  Expect about a dozen compressions to complete the job.

And again, if you do not intend on checking the Oil Level, there is no need to Burp the engine at all.  Just start it!

Thankyou for your response, i was under the misunderstanding that it was either relieving air (burp) or purging oil out of the top of the engine, you can tell i have much to learn!

I've done the slow turn & mine starts gurgling almost immediately, but what i have noticed esp. when its cold, (< 70*) it seems to start easier w/ less gearbox banging about.

Im still puzzled why the oil level goes down w/ burping.

We're lucky to have you and Roger assist us understand a bit better our wonderful engines.