Rotax 912 burping procedure

[Dave S]

Hi all,

Maybe everyone else already knows this, but it apparently took a while for me to figure it out.

It's seems to be true that burping the engine oil system when it is cold (like zero F or thereabouts) takes a lot of revolutions to push all the relatively thick oil back into the oil tank.

If I check the oil level right after shutdown...it is definitely down the dipstick so some of the oil is not in the oil tank at that point.

But...it takes very few revolutions of the prop to burp it when it is warm after shutdown.

I found that by burping the engine not too long after shutdown, the oil appears to stay mostly in the oil tank afterwards; and, it only takes one or two revolutions to be sure the burp is complete after the engine is stone cold a day or more later. The oil level appears to stay up in the oil tank after a warm burp.

Wondering if this is similar to the experience of others; or, if this works only in certain installations?

Thanks,

Dave S
KF7 Trigear Flying
912ULS, Warp Drive

[HighWing]

I found this the case as well, but it was with the high mounted tank on the Model IV. I supposed that lots of turns meant good ring seal and low blow-by. I am curious now because of the low mounted tank on the 7. My new IV has the tank mounted low and assumed that any oil movement over time would fill the tank rather than siphoning from the tank. I do notice that when cranking, it takes a few seconds longer to see the oil pressure gauge needle move with the low mounted tank.
Lowell

[Av8r3400]

If you are using the latest and greatest Rotax oil filter with the anti-flowback check valve, the post flight burp *should* keep the oil in the tank on a high mounted oil tank.

[wwillyard]

The new style oil filter from Rotax helps keep the oil in the high mounted tank longer, but it will still drain down over longer periods of no use.