My model 4 912 uls with the high mounted oil tank take on average 100 blades to burp after sitting a couple weeks. Engine compression is fine with 900 hours total time.
My model 4 912 uls with the high mounted oil tank take on average 100 blades to burp after sitting a couple weeks. Engine compression is fine with 900 hours total time.
DesertFox4
Admin.
7 Super Sport912 ULS Tri-gear
I am just thinking out loud here, but my understanding of the burping is a buildup of pressure in the crankcase due to piston compression leaking past the rings into the crankcase. That is why if you dwell on each compression stroke it will burp faster, also why a hot burp works faster. Maybe your friend's older engine has lots of crud built up on the rings and ring gaps and therefore does not leak compression gas past the rings very fast, especially with cold thick oil. Also the valves may not be sealing as well and leaking out into the exhaust and intake if the compression feels low. Just some thoughts.
Jim Ott
Portland, OR
Kitfox SS7 flying
Rotax 912ULS
I had the same issue. It turned out to be a "non-issue". I have a model 4 with the high mounted oil tank. The engine is a '95 brand new engine that like DesertFox needed 100 blades and more to burp. I thought something had to be wrong so I tried everything I could think of to cure it. Compression check showed 80lbs, I purged and repurged, looked for leaks but nothing helped. Oil pressure came right up spinning with the starter. Finally I called Roger Lee. If you're not familiar with him, he's well known as one of the sharpest Rotax people out there. I can personally testify that he's also one of the nicest. He assured me that nothing was wrong. It's basically the high mounted oil tank. His advice is to pull it thru a few times to check for hydraulic lock when cold. Go fly and burp it and check the oil afterwards while it's hot. I've followed his advise and this works fine for me. My engine runs great. James Thomas
I forgot to add he's using a 'different' oil ? other than AS Sport +4. And a Tempest filter. So all of this prolly adds up to making it more difficult to burp. Propping it hot is the way to check it. Most likely nothing wrong with the engine at all. Great feedback!! Thanks you guys.
Great to hear you're almost finished, Jim!
my feeling on this, I can care less. I don't usually burp before run. I will turn my engine over about 18 compression strokes and then get inside and turn it over until the oil pressure comes up with mags off. that's it. if I want to check oil level, I do it after a flight. I shut the engine off, pull out the stick, it WILL be at the proper level.
I will burp the engine before changing oil, I don't pre warm the engine. If I happen to do an oil change in real cold weather, I plug in the engine warmer.
another note: If you want to burp the engine with better results, remove the oil canister lid. I've have noticed that the burp will happen a lot quicker.
steve
slyfox
model IV 1200-flying
912uls
IVO medium in-flight
RV7A-flying
IO-360
constant speed prop
I check the oil after the flight.
Pull 15 blades to make sure engine not locked before the 1st flight of the day.
If there is not a puddle of oil on the floor, it is still where it belongs.
I started wishing for a Lycoming if 100 plus blades before burp were required.
Good idea Slyfox to see oil pressure before letting it start