Sounds like a problem with your float needle, but I can't imagine that a new carb would have that problem.

It could be that due to age or bad fuel in the past that the fuel line is breaking down internally. Pieces of rubber could be breaking off and entering the carb, hanging open the inlet needle. Cleaning out the inlet needle and a new fuel line may take care of the problem.

Ditto what Walrus said. I've done carb jobs and had the carb immediately leak because a chunk of crud was broken loose and wasn't flushed from the fuel line before reinstalling the carb. I figured it out after the second one leaked.

Here some places I have found this problem start at top fuel supply can rust flaking off inside gas cap even if part metal rust flaking fitting bottom of tank rust flaking I found once on plastic tank with elbow fitting of steel rust flaking small pieces is all takes. We use containers to long I buy 10 gallon gas can in 2005 its begining to rust inside. I may can rock and roll it use one more season.

Are you sure its leaking from inside.
Seems more like a old fuel hose cracked at the end.