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Why Burp Rotax 912ULS?

jnmeade

Well Known Member
We've all been taught to "burp" the Rotax 912ULS to move the oil from the crankcase to the oil tank so that we can accurately measure the oil level. Here is a nice technical discussion of what happens.

https://electricmotorglider.com/201...tricMotorGlider+(EMG-6+Electric+Motor+Glider)

In addition to moving the oil from the crankcase to the oil tank, some hold that "burping" enough blades also tests for hydrolock. Hydrolock seems to be a phenomenon that is very rare in a flat, opposed engine. I've never been taught or seen any emphasis on testing for hydrolock in a Continental, Lycoming, Franklin or any other flat engine I've flown, so I'm going to assume that testing for hydrolock is not a necessary reason to "burp" a Rotax 912ULS. If that is in error, please give me the reference so I can learn.

When we fly an IO360, we likely know that it will hold 8 quarts of oil and that it is required by the FAA to fly all day on 4 quarts. Many of us don't even put in 8 quarts, rather, we use 7. Many don't add oil until the dip stick shows 6 quarts or even 5 quarts. The Rotax 912ULS has a range on the dipstick that is acceptable for oil level. So it does not seem critical to have some maximum or close to maximum oil level.

The following assumes this is your aircraft, you are the only one flying it and you know the oil fill history. That means you added the 3 liters at oil change time and noted any other additions.

Now, you go out and check your engine cold. It is at or above the add mark. You know there is zero or some additional oil in the crankcase so if you "burped" it and transferred some or all of that oil to the tank, the oil level in the tank would be equal to or greater than the oil level you measured "pre-burp". In other words, in this example, enough.

We have established that the oil tank contains enough oil and we are reasonably sure since we manage the oil that it does not have too much.

Why burp?
 
Good question. I rarely burped mine because it didn't leak a drop nor did it burn any. I checked the level cold because I knew where it would line up.

I'm not sure the Rotax docu would approve but that's what I did.
 
I don't think you have to burp the engine if you are the sole operator and know where the oil level is.

However, consider that the engine is a dry sump design, in fact there is no sump as such, and if you do a cold start the crankshaft may have to spin in cold viscous oil unless you have moved it out to the oil tank. Also, it can't hurt to turn the prop and pre-pressure, pre-lube the bearings. I know the Merlin engines have a pre-oiler that is run before start-up, but of course the 912 is not a Merlin. ;)

Anyway, I like doing the burp routine, gives me a chance to bond a little with my girl before flying.
 
I have been told it's not good to turn over the prop of Continental and Lycoming engines by hand because you just dry scrape the cylindar walls without doing any good - better to get the pump turning fast and get some oil moving.

I'm not inclined to think turning the Rotax over by hand lubes anything. It would be good to hear some definitive info on that question.
 
I have been told it's not good to turn over the prop of Continental and Lycoming engines by hand because you just dry scrape the cylindar walls without doing any good - better to get the pump turning fast and get some oil moving.

I'm not inclined to think turning the Rotax over by hand lubes anything. It would be good to hear some definitive info on that question.

I don't get even close to a prop on a Lyc. or Cont. The 912 is a different animal entirely. She doesn't have magnetos so hand propping probably won't kill you.

You can see oil pressure on the gauge when you prop it by hand so oil must be moving through the bearings. I don't know about dry scraping the cylinder walls, but Rotax recommends burping the engine to check oil so their engineers are OK with turning it by hand.
 
You see oil pressure on the gauge when hand propping the Rotax 912ULS? I'll have to do that and see. If it does build oil pressure I have no objection to that. I'm not sure it's necessary or even useful to "pre-lube" the bearings, though. Thoughts on that?
 
It's funny how new people to Rotax have never studied Rotax history and know nothing about its history or engine and part specs. Knowing about 10 engines isn't like getting info from world use.
Do Rotax engines get hydrolock. Yes. Back when the Kitfox aircraft always mounted their oil tanks too high and when using the old Rotax oil filter they had hydrolock issues. Even though Rotax has changed their filters over the years to help prevent that it still happens to some engines. A friend of mine went to do a pre-buy last week on a Sport Cruiser. Before they started it they went to rotate the prop and it came to a stop. They removed all the bottom plugs and oil poured out of the #2 cyl. If they had turned the key that would have bent a lot of expensive parts. That bill would have been around $8K+. The had another about a month ago in Texas. Hydrolock issues have been greatly reduced over the years, but they can and still do happen occasionally. Some gambles might be worth it to some folks, but some aren't. If you want to play gamble better just head to Las Vegas.

The oil level check is not as accurate as some have been led to believe. It certainly puts you in the ballpark, but it can lie to you and usually on the low side. You are right that rotating the prop should make it only go higher on the stick because the oil that has settled in the bottom of the case gets pushed on back to the tank with air pressure.
 
Another note from experience - -

I have found that if you spend a little extra time taxiing to shut-down, it seems to leave a little more oil in the engine. My theory is that while warm, there is less blow-by, and if you use very light throttle getting to shut-down, maybe not as much oil gets pushed back to the tank. I like to check the oil level by burping right after shut-down. Takes less amount of turns, and you don't have to check it next time if no oil is on the floor. The RV-12 design I don't believe will cause hydro-lock. Anyway, my story - - -. Over-filling because you did not burp it will waste oil, because it over flows any extra you put in. I try to keep level about mid way on flat of stick.
 
Jolly, you wrote the following less than a year ago: "Just saw this on the Rotax Owner forum. A new service class for Rotax annuals and inspections that is supposed to be all hands on. Might be cool to go to. I'm a newbie so I think I'll go. I can use the help on my 12 and I need to know more about my engine."

Funny, you don't seem to be such a newbie, based on your comment earlier today (see #8, above). So, how is the "12" build coming? What's up with the mystery?
 
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Jolly is Roger Lee. He'e been on here before with other user names. He hangs out at CTFLIER and Rotax Owners.
 
Hi Jim,
You're the second person to accuse me of being Rodger. Sorry, but I live in CA. and when I met him at the Rotax class he lives in AZ.
 
Hi R100rs,
Only a newbie with my RV12. I've been using Rotax engines since 1980. 503's in ultralights, 582's in Gyro's and then the 912 in all my other aircraft. Started taking classes about 2 years ago. I have a good friend that teaches Rotax out of BC, Canada soil have a good info direct line. I made a point of reading all the 912 manuals cover to coverand that was a great help. I'm not on here very often, but when I see an odd question I call my friend.
 
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Jolly, of course, the old "asking for a friend." Your pal in BC gave you a whole lecture on every case of hydrolock in America just so you could answer a question on Vans, right down the dollar value of the repair. Really?

And, even though you are a "newbie" ("I need to know more about my engine"), you thought it was appropriate to condescend to the rest of us about Rotax history and the like (see your own comment above).

Hard for me to believe that your story isn't nonsense. IMHO, you are insulting the intelligence of everyone on this site. Really, why were you advertising for the Rotax class, anyhow?
 
Wow, we're going to need Robert Mueller to be special counsel investigating who is the clandestine poster in the "Why Burp Rotax 912ULS" thread... :eek:
 
I know how to solve this. If we can find the FBI agent that busted the Unibomber we could have him do a writing style analysis between Roger and Jolly.
:)
 
Hi R100rs,
Sorry if you took that post as condescending. It was not meant to be.

I was just trying to offer a different opinion based on some real time issues and expertise.
I read post and get interested in an answer and I call my friend. Best way to get a good solid answer. The other thing I do see in some people that seem to contradict Rotax or Bing, is failing to do good research that usually needs to go back as far as 1990 to understand why some things are as they are. I'm a big believer in knowledge and education. I've thrown myself hard into over the last couple of years.


I was told Burping the engine comes from a long history of why you should and sometimes what happens when you don't and why with Rotax's experience they still want it done. Even if you don't check your oil it only takes a few seconds to rotate the prop a turn or two to check for oil in the cylinder and this might save you thousands of dollars. Kind of hard to argue against something that takes seconds, easy to do and may save you a lot of heartache.
 
Jolly, enough. Playing VansAirforce users for fools is annoying.

You are either a newbie who wants to take classes to learn more about his 912 or you are an expert who lectures us about the benefits of "burping" and the failure of 912 owners to brush up on Rotax history. You can't be both at the same time, which is exactly what you have tried to do. The "call a friend" dodge is laughable.

Also, in my opinion, your writing style bears a remarkable resemblance to an expert who teaches Rotax classes and who writes on a forum devoted to another airplane brand. What a coincidence.
 
Things eventually begin to catch up with people that make up story's..........

I have had PM exchanges with Jolly (Roger.... notice the possible connection there?)

Jolly's profile says his name is Brad. When he has PM'ed with me privately, he has said his name was Mike. (???)

He at one point has talked like he owns a different brand LSA (Flight Design CT perhaps?) but more recently his posts say he owns an RV-12.

His profile says he lives in San Francisco.

There are no FAA registrations for an RV-12 in the name of Brad or Mike, in San Fran. or anywhere else in southern CA.


I would be the first to admit that Roger is very knowledgeable about the operation, maintenance, and repair of Rotax engines. I have benefited from info he has shared in the past.

The down side to Roger is that he presses his (sometimes incorrect) opinion even when there is a multitude of people trying to provide the correct info.
If he wants to do that in other internet forums (and they are willing to put up with it) that is fine.
Here in the RV-12 forum I think it is safe to say that the common goal of everyone who posts is to pass on what they have learned to those that are new, so they can learn it the easy way instead of the hard way. Because of that, him repeatedly posting his incorrect opinion should not be tolerated.
Everyone is entitled to present their opinion in a civil manner, but when you continue to argue your point even when it is directly contrary to the info published by the kit manufacturer, it does nothing but cause confusion for all of the new people that come to the forum for help.

Roger Lee's original user account was closed by Doug (about 3 years ago) when Roger decided to have a wrestling match with him over his forum policies (advertising his business in his signature but not being willing to be a paid advertiser).

Since that banning, Roger has continued to show up using at least 3 different alias's that I am aware of (yes his writing style and the subject matter that he tends to trigger on is quite specific). Often times his posts are for the primary purpose of still promoting his business by advertising / announcing an up coming Rotax class he is holding, or promoting his LSA fly-in, etc., without being an advertiser.

P.S. I, nor anyone else at Van's had any involvement in him originally being banned. It seems it was simply Roger being Roger, and thinking he could do or say what ever he wanted here in the forums, even if it was in direct conflict with Doug's forum rules. Doug saw it differently.
 
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