On the brass jet block there is an alignment peg that fits into the body of the carburetor. Above this peg and a little to one side is a hole that passes completely thru the jet block. When the jet block is seated in the carburetor body and the mixing chamber union nut is firmly seated the small hole is still partly visible in the slot of the carburetor body.
I have some questions:
1. What is the purpose of this exposed hole?
2. Should gasoline come out of this hole?
3. What is the problem if gasoline does out this hole?
Petrol will leak out in that area if your float needle is not sealing on its seat properly or if you have a hard gasket below the jet block that fits inside the big nut. You need a crushable gasket. You may get away with gently lapping the float needle with brasso or other fine paste. Valve grinding paste is too coarse.