Hi Chad .....congratulations on your new Alon. Great plane. You've gotten some good answers already and I probably can't add to them.
I had a late serial no. Coupe like Wayne described, with unvented wing caps.No problems. I had an Alon. Problems. The Alon has the same closed system as the late serial Coupe, also with unvented caps. Alon issued several Bulletins on this fuel system. I'd suggest calling the previous owner and asking him what problems he had and if he has the bulletins. I found them informative but not very helpful. I think Roger's explanation is the answer. And it applies whether you are talking about vented or unvented caps. With one tank negative the results are the same if the other is positive or zero, just the degree. And, of course, after the gas burns down and you no longer see the over- flow the negative pressure effect continues. Jolly's advice on gaskets is important. I used the red gaskets with the lubricating rings. I, too, found gasket thickness and tang adjustment very important. Alon's final solution was to recommend "thermos bottle" type wing caps. When in place you push a lever to seal. I've seen them on some Alons but as I recall most use regular caps. I tried one (the're expensive) but wasn't satisfied. I finally solved my problem with unvented caps, good gaskets and fueling precautions. I still would find one tank slightly lower than the other. Also I'd measure wing distance to ground on a level surface to see if one wing is lower. If so this aggravates the problem and requires special fueling precautions. That was part of my problem. If you feel that you might have a fuel flow restriction as Jolly suggested E-MAIL me and I'll send you a simple 3 step process to check it. Stay with it and talk to lots of Aloners.Good Luck......Cliff
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