First , that carb is NOT gravity fed ... if you note the first pic , where the nipple is coming up from . THAT is a diaprahm pump under there . And if you also note the little hole on the side of the carb that bolts up to the engine ... its called a PULSE HOLE ... this is where the vacuum from the engine comes thru and pulls on the carbs diaphram pump , causes the fuel to be SUCKED into the carb .
Now , you MIGHT need a new diaphram , seeing as to how a LOT of folks leave fuel in the them when they shut the weedies down which in turn literally stretches the little diaphram inside and causes it NOT to pump/suck the fuel a needed . ( new carb kits contain them )
And as far as the HEAT DAM ( little black plastic thingy that goes between the carb and the engine ) , simply get yourself some JB WELD and go at it with that .... will hold your nuts in place and make sure you CLEAN , and then clean again , the area where you are going to use it .... ( even though JB is NOT affected by gasoline AFTER its cured , it WILL NOT bond to surfaces that are impregnated with oils ( gas ) , so buff it , then use some good cleaner on it after buffing , then toss on your JB , throw a little heat to it ( for better curing - I use an old hir blow dryer ) and wait 24 hrs , then WHA LA .... done .

EBAY.... do a search for WALBRO and the go to the following link to check the numbers ( carb model ) and check the venturi size ... do NOT go over anything larger than a 9.0 venturi for that stock engine
http://wem.walbro.com/walbro/family2.asp