Possible tank leak search help needed.

[Wheels]

Ok, to muddy the waters, I do have glass visible filters in my line from tank to header. I also have a vent line to each tank. I fly it and can visually see what's happening and have run several dozen tanks of fuel through the system. The extra vent solved a problem with excess fuel being overboarded through the single vent into a single tank and giving me an asymetrical fuel load in flight.

You probably can over filterize (I just made that up) but to leave out essential filters is a no no. Bing carbs don't like dirt. (check the forum)
I have an inline filter at the tank, a gascolator, finger strainers for the big stuff in the tank, and whatever else comes organic to the carbs and fuel pump if anything.
I used the in line filters because of the old sloshing compound that was coming off my tanks. Now I have new tanks and thats not an issue but I like seeing if there is any crud in my fuel before it gets to far down stream.

[beeryboats]

Ok, so I'm not crazy on the filter idea. I don't see any sloshing compound in my tanks from the filler, but I plan on endoscoping the tanks tomorrow. I'm still not understanding your issue with only the one vent though.

[kitfoxnick]

I have glass filters that can be seen thru the turtle deck. These filters come apart to clean, and have a fine mesh filter. I like being able to see if I'm getting any crud out of the tanks. I would not recommend the use of paper filters.

[Micro Mong Bldr]

Only 1 vent has the potential to cause uneven flow, you have to plumb the vent to both tanks if you have only 1. Probably easier to just have 2.
Cheers,
L

[beeryboats]

L,
I don't know how that could happen when both caps have air pressure tubes pointed forward. I noticed that the left tank has what looks like a poor mans fuel gauge. It's a piece of 1/4" clear tubing that goes from the bottom to the top of the tank. But the builder also left large sections of the end of the tank unpainted with fuel level marks in felt pen.

I took a couple videos with my endoscope of the inside of the tanks. I don't know what to think. I see what appears to be large pieces of epoxy that I can move by thumping the underside of the tank. And on the left side I also see what looks like an area of flaking paint. But that could be just epoxy sticking up too. I was looking for fuzzy fibers and didn't see anything like that at all. I think I'm going to go with in-line filters, at least for a while, and see what comes out of the tanks.

[Wheels]

Ok, John Mcbean, slap me if I use the wrong word again. Vent line or Return line are two distinctly different components to the fuel system.
When you add the rotax recommended return line to your system, you are giving a route for excessive fuel to be "returned" to the tank. The fuel pump is capable of delivering more fuel than you will use during operations and the return line allows the excessive fuel to go back to the tank rather than be pressure pumped into a carburator that doesn't need it and cant burn it all.

As the fuel returns to a single point, EXAMPLE, left tank, the left tank ends up with more fuel than the right tank. (DUH) On a long flight, say 3 or more hours, it is not abnormal to see one tank at 1/4 full and one tank nearly empty. So I simply added a y connection at the return line from the header tank. I put in a return to the left and one to the right tank. Now excessive fuel is symetrically pumped back to my tanks and I don't see the difference in my fuel load during a long flight. I did this to a set of brand new Kitfox supplied ethonol resistant fuel tanks before I installed them. My Mechanic "friend" used all brass fittings.

Fuel Vent/ is the forward angled tubes on top of your wing and yes it allows ram air to lightly enter your fuel tank to keep possitive pressure in your fuel flow while simultaeneously giving your fuel system a breath of air to keep VACUME from occuring in the system. (Put your finger over a straw and suck through the other end, nothing moves. Open the "vent" and you have flow.)
If you turn them backward, you will create a vacume problem and life can become interesting in a short time, or it could end in tragedy. So, to recap, Vent is air, return is fuel. whatdoyathink? I am unsure about the condition of your tanks but it sounds bad, can you send pics?

[beeryboats]

Thanks for the info, but I'm wondering if we have the same set-up. I have the 582 Rotax two stroke, and from what I've been able to see so far I have a feed line to the header tank from each wing and a header tank vent that goes back up to the right tank. I've been able to trace the fuel system up to the firewall so far, but I just got things moved around so I could get the cowling off. From what I saw yesterday I see the fuel line go to the fuel shut-off, which broke when I turned it, then to the gascolator, then to the fuel pump, then two lines go into the mess of stuff around the carbs.
I'm touching anything else until I can get some photos taken. But I see nothing like a return line. I work at a diesel shop and I'm very familiar return fuel systems. I see nothing like that.