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  #11  
Old 01-14-2021, 08:09 AM
bobg56 bobg56 is offline
 
Join Date: Nov 2018
Location: Peachtree City, GA
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My cold oil level before burping is right about at the lower edge of stick, after turning slowly at each compression bump it comes up to about the full line (1/4") from it....so I know that if my cold oil is at lower edge its good to go, checked it this way many times and I do recheck after flying and due to expansion the level will hit the full mark or slightly over, it seems easy to over service so I'm very wary before I add any oil.
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  #12  
Old 01-14-2021, 08:28 AM
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Champ Champ is offline
 
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Please excuse my ignorance. I have never heard of burping an engine. How do you do it? Is it specific to Rotax engines? Should I be burping my Lycosaraus clone?
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  #13  
Old 01-14-2021, 08:36 AM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by Champ View Post
Please excuse my ignorance. I have never heard of burping an engine. How do you do it? Is it specific to Rotax engines? Should I be burping my Lycosaraus clone?
You have a lot to learn... Rotax is very different than 80 year old Lyc and Cont designs.
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  #14  
Old 01-14-2021, 09:35 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by NinerBikes View Post
The burp when cold is for Rotax engines mounted in other planes, such as taildraggers with Bush tires on them. Sometimes, this configuration causes problems with the fuel floats in the carbs, also, since the engine is not close to being level.

In some situations, such as on some Kitfox builds, the sump tank is mounted so low on the firewall, such that the oil can syphon back into the engine or back cylinder heads and cause hydraulic lock.

So turning the prop after sitting or in your hanger, ensures that there's no hydraulic lock that could bend connecting rods or do other damage to your engine, before you use the electric starter.

I do get two different readings, if I only burp when cold, it's shows up lower on the dip stick, sometimes as much as 3/16 to 1/4 " difference.
I think Hyd lock on a 912 Rotax is an urban myth. There is not enough volume in the tank to fill the engine enough to cause it unless your hangar is built on the side of a hill and not level. And a low mounted tank would reduce the tendency for oil to be siphoned from the tank to the engine case. If anything, the RV-12 would be considered to have a rather high mounted tank (within the range allowed by Rotax's specifications).

The document on our web site (here is a link that works - https://www.vansaircraft.com/faq/bur...eck-oil-level/) explains it pretty well. Some of the observant experts will read it and say "The oil doesn't get pumped from the engine back to the tank. It is pushed by positive crank case pressure." Yea, I know that. The description was used to explain the process in simple terms, to those that are unfamiliar with a 912 Rotax.
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Last edited by rvbuilder2002 : 01-14-2021 at 09:37 AM.
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  #15  
Old 01-14-2021, 10:27 AM
NinerBikes NinerBikes is offline
 
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Location: Granada Hills
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Quote:
Originally Posted by rvbuilder2002 View Post
I think Hyd lock on a 912 Rotax is an urban myth. There is not enough volume in the tank to fill the engine enough to cause it unless your hangar is built on the side of a hill and not level. And a low mounted tank would reduce the tendency for oil to be siphoned from the tank to the engine case. If anything, the RV-12 would be considered to have a rather high mounted tank (within the range allowed by Rotax's specifications).

The document on our web site (here is a link that works - https://www.vansaircraft.com/faq/bur...eck-oil-level/) explains it pretty well. Some of the observant experts will read it and say "The oil doesn't get pumped from the engine back to the tank. It is pushed by positive crank case pressure." Yea, I know that. The description was used to explain the process in simple terms, to those that are unfamiliar with a 912 Rotax.
It is believed there were Rotax oil filters or off brand oil filters produced that did not have the anti siphon valve feature included, used on some Rotax equipped planes, which caused the draining of the oil sump, on several far from level tail dragger model tube framed airplanes, some aggravated by big bushwheel tires with the angle of pitch.

So I've read... could be urban myth, or not. It's not like a Rotax is a Lycoming Wasp or other Radial engine that needs the prop spun for the same reasons of gravity and the bottom cylinders.
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Last edited by NinerBikes : 01-19-2021 at 10:27 PM.
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  #16  
Old 01-14-2021, 12:09 PM
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Quote:
Originally Posted by Piper J3 View Post
You have a lot to learn... Rotax is very different than 80 year old Lyc and Cont designs.
Talked to a local AME who explained the procedure and reason for burping a Rotax.

Also a procedure for “burping” a Lycoming or Continental induction system to check for leaks.

You don’t learn unless you ask. Learn something new every day.
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  #17  
Old 01-18-2021, 11:41 PM
DaveWelch DaveWelch is offline
 
Join Date: Mar 2005
Location: Huntsville, AL
Posts: 447
Default No worries

Learn on Champ! And ask away.
We all started new at this.
Some of our “experts “ may sound a bit “crusty” but we’re well intended.
Most of all have fun.
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  #18  
Old 01-19-2021, 06:27 PM
Dan92 Dan92 is offline
 
Join Date: Nov 2007
Location: Lake City, FL
Posts: 103
Default Burping

Hydraulic lock on a Rotax is NOT an urban myth. I have had it happen two times although it was not on an RV. Dropping the bottom plugs drained the oil that was causing the problem. Keep on burping to check for that.

Dan
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  #19  
Old 01-19-2021, 10:32 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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I used to own a Yak-52 with a 9 cylinder radial. The mystique of a radial is half the fun of owning one. If you have ever seen the WWII films of ground crew pulling though radials know that it is real part of preflight. Usually it was a futile ritual, but sometimes I would find the prop came to a stop. Rocking the prop back and forth would puke a cup or two of oil out the exhaust. I’ve never encountered that in 35 years flying horizontally opposed engines. However, get oil in the cylinder and it will lock.
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