ORIGINAL: abacro
The solution is a simple fix. Remove the diaphram cover ( the one with the 4 small screws) and adjust the needle seat a tad lower. Your loading the low end up because it is set to high. On the Sach's 4.2;s the diaphram sit;s on top of the carb with the engine mounted inverted,and with the high needle setting,it will gravity feed through the carb asnd out the butterfly opening.
hope this info helps
Art
I was going to give this one a thumbs up but the RCU smileys are all effed up...again.
If it's leaking fuel from the carb venturi the above is the answer. The needle is not seating to close off the main fuel passage.