912ULS won't burp

[DesertFox4]

I started wishing for a Lycoming if 100 plus blades before burp were required

100 blades is normal after sitting a couple weeks especially on a model 4 with the higher mounted tank. Seen this on brand new Rotax engines and is no indication of engine health either way as jrthomas stated after talking with Roger Lee, so not sure what is implyed by the statement in quotes above. Roger is not the only highly experienced Rotax mechanic to confim this normal Rotax specific characteristic.

I've also found the most accurate oil level readings come from post flight checks and if you are flying as often as someone like slyfox then his described pre-start procedure works well and I have employed it many times. I find with my building taking precedent over my flying lately that long periods of inactivity require burping pre-engine start just for piece of mind.

[Dusty]

Re:burping post flight
This is defiantly the quickest way and the oil level difference between hot and cold is minimal.However I can't bring myselfe to NOT check the level on preflight but a few blades is then all it takes to reburp.
(KF4 high tank)

[jiott]

I found that you can really reduce the number of blades to burp, even on a cold engine, if you dwell on each compression stroke-just hold the blade against the pressure, maybe very slowly turning it to hold the pressure until the pressure bleeds off and the blade will turn easily to the next compression stroke, and repeat. Its not the rate or speed or number of blades that matters, but rather the time held against compression to cause blowby past the rings into the crankcase. This eliminates the frantic blade turning on the ramp which makes everyone wonder what kind of weird engine is that. Of course most of you already know this, but maybe some new to Rotax haven't figured it out yet.

[Slyfox]

yes I agree, take it slow at each compression stroke, but like I said, make sure and remove the cap off the oil tank. That made a difference when burping mine.

[jiott]

If the cap is on the oil tank I have trouble hearing it burp; cap off no problem at all.

[Av8r3400]

Using the described compression dwell, cap off method, I have never had to pull more than 15-20 blades, cold, on either of my high tank Model IVs.

[jiott]

Come to think of it, the faster you turn the prop the more oil you are pumping out of the tank, thru the system and back into the crankcase, which slows down the process of blowing oil out of the case back to the tank, which then takes more blades to empty the crankcase and burp. Kind of self defeating. Slower turning with dwell is just the opposite, which speeds up the whole process.

[PaulSS]

My first post, so be gentle

I had to Google Rotax 'burping' as I had no idea what you guys were talking about. I don't (yet) own a Kitfox, or any other Rotax-powered machine for that matter, but have flown behind one in the Tecnam and still had no idea. My Googling led me to this Youtube video, which I think gives some good ideas of what, why and how. Enjoy your burping:

Burping Rotax

[jiott]

Paul you better hurry and order your own Kitfox! What better thing could you do where public burping is not only socially acceptable but mandatory.

[PaulSS]

Haha, believe me; I'm looking. I've seen a IV that looks great but has the straight 80hp engine. IF I take the aircraft back to England then I reckon it would be flown from a very short farm strip, so now I'm all over the Zipper modification and trying to find out the state of slipper clutches, beefed up starter motors etc (I'd like to convert it to 115hp just to give me more options). I knew literally nothing of this until a few days ago but have had some down time in China, so this website has been thoroughly viewed.....my eyes are sore from so much reading