Bing 54 Carb - Small Fuel Inlet Fitting

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

ClaudeR

Active Member
HBA Supporter
Joined
Jul 22, 2020
Messages
25
Location
KSMX
Hi, all:

I recently purchased an older US Light Aircraft Hornet airplane that has a Hirth 2706 and Bing 54 carbs. It has sat awhile, so I'm going through it and upgrading/replacing stuff. One thing I noticed is that where the fuel line connects to the Bing 54 carbs, the inlet barb is too small for 1/4" ID fuel line. When I removed the fuel line from the carb, I at first thought that the inner portion of the fuel line had peeled away and remained attached to the fuel inlet fitting. But, I discovered later that instead a small piece of smaller tubing had been previously installed and then the 1/4" ID fuel line attached over that. Here's a picture of the small piece of tubing left on the fitting after the main fuel line had been removed.



So question(s):

  • Is this the correct way to attach a fuel line to a too-small-for-the-fuel-line fitting? It seems to me that it would be far to easy for the fuel line to disconnect, but perhaps I'm wrong?
  • Is a fuel fitting for the Bing 54 carb that would fit 1/4" ID fuel line available? I searched but could not find one. Perhaps it's out there but not shown as being specifically for the Bing 54?
  • Assuming I need to replace the existing fuel fitting, how is the existing fitting removed? I tried wrapping the fitting with some protection and using pliers to unscrew it but it wouldn't budge. For example, does the carb need to be fully disassembled and the fitting heated to soften a thread locker like Loctite? If so, when installing the new fitting (assuming I can find one), which Loctite product would be used?
Thanks in advance for any help.

Claude
 

akwrencher

Well-Known Member
HBA Supporter
Joined
Oct 16, 2012
Messages
1,394
Location
Gustavus, AK
I don't know much about Bing carbs in particular, but most small carbs do not have fuel inlet fittings that unscrew. They are typically pressed in. If it doesn't have a hex spot for a wrench, I would hesitate to try to remove it without further info. Also, no, using a smaller tube is inside is fine on a lawnmower. But your instinct is correct, not a safe install on an airplane.
 

TiPi

Well-Known Member
HBA Supporter
Log Member
Joined
Aug 25, 2019
Messages
480
Location
Peeramon (AUS)
The photo doesn't show, can you please re-post it?
The Bing has 2 connections: one is the fuel inlet and the other is the vent line. The vent line is about 4mm ID. The fuel inlet fitting is pressed in and should be either 5mm or 6mm.
What size is your hose barb fitting?
1626180239671.png
 

ClaudeR

Active Member
HBA Supporter
Joined
Jul 22, 2020
Messages
25
Location
KSMX
Hi.

I'm not at the hangar and probably won't be for a couple of days, so here's what I remember and some thoughts.

I saw the vent tubes going from one side to the other on the carb (and with a small hole in the middle) and realize that it would be much smaller than the fuel-line connection. FYI: In the picture that I included in my original post the vent tube is shown above the fuel inlet connection.

TiPi> What size is your hose barb fitting?

I don't know exactly, but I do know that it is smaller than 1/4". When I placed a short piece of 1/4" fuel line onto the fuel inlet connection (hose barb fitting) it can be easily moved up and down without much effort at all (two fingers lightly holding onto the fuel line).

FYI: Here's another picture this time with the small piece of tubing removed from the fuel inlet connection. You can also see here that the fitting design is different than a normal barbed connection what with two ridge-lines (for lack of a better term, maybe rings would be a better term) and a rounded section at the opening of the fitting rather than the more traditional (at least to me) barb(s).



akwrencher> ...are typically pressed in. If it doesn't have a hex spot for a wrench, I would hesitate to try to remove it without further info. Also, no, using a smaller tube is inside is fine on a lawnmower. But your instinct is correct, not a safe install on an airplane.

So, unless someone can point me in a different direction, sounds like:
  • The way of connecting the fuel line to the carb using a small tube under a larger tube is wrong and needs to be changed (BTW: based on what I see in the first picture (original post) showing some discoloring under the small tube on the fuel line fitting, I suspect that it was not sealing well and that's an indication of leaking fuel/oil mixture getting under that tube).
  • Changing out the existing fuel line connection fitting on the carb to a proper barbed and sized fitting is probably not an option.
  • The only option then that I can think of is to use an adapter/converter (probably 5mm or 6mm on one end and 1/4" on the other) that a very short piece of the smaller tubing connects to on one end and the main fuel line (1/4" ID) connects to the other.
Any other ideas?

Thanks for your help!

Claude
 

MACOWA

Well-Known Member
HBA Supporter
Joined
Apr 19, 2021
Messages
52
Hello, Claude. Use REINFORCED black rubber fuel line, it will be marked
"1/4 fuel line" right on it. Just pushed a piece onto the 54 in my lap, rock solid perfect. replace the whole line. Your local outboard store will have what you need. After all five bucks is cheap insurance.
 

ClaudeR

Active Member
HBA Supporter
Joined
Jul 22, 2020
Messages
25
Location
KSMX
Thanks for the reply.

Is your fuel barb the same shape and size as mine? Mine is smaller than 1/4" (closer to 3/16" ... 1/4" fuel hose slips over the barb with almost no friction). What I have done so far is add an 3/16"-1/4" adapter with a small piece of 3/16" hose. Here's a picture FYI.

 

TiPi

Well-Known Member
HBA Supporter
Log Member
Joined
Aug 25, 2019
Messages
480
Location
Peeramon (AUS)
this is the most sensible option unless you are game enough to remove the old fitting and press in a new one with the 1/4" tail.
 

MACOWA

Well-Known Member
HBA Supporter
Joined
Apr 19, 2021
Messages
52
Hello, ClaudeR. Commercial clear tubing measures exactly 1/4" ID. 1/4" Reinforced fuel line measures 3/16" ID. When it expands over the barb it's tight, after all its rubber. I own six Bing 54"s all fuel inlets are the same.
 
Top