RE: New mcd cy motor tuning trouble(gas tank)!
if the fuel tank level has anything to do with how it runs, about the ONLY thing it can be is a bad fuel line to the clunk. these carbs have fuel pumps, they are capable of pumping fuel from a good 4 feet below the level of the carb
I say rebuild the carb and get some new fuel line, for the carb, go to a small engine shop and get a D10WAT rebuild kit, their fuel line is probably going to be expensive though (I was quoted $5 or so a foot, but I had no money back when I asked then...), so might want to go to a hobby shop for that