the screws are as tight as I can get them.
Thats part of the problem.. Over tightening the screws will bend the tabs over, so the hole carb sits up off the tank in the middle, because the tabs are all bent over..
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.check out this thread...
http://www.oldminibikes.com/forum/b...s/59393-tech-trueing-your-diaphram-cover.html
You have to use a file, or like some real heavy grit, heavy duty sand paper, laid on a perfectly flat surface, then grind the bottom of the carb flat..
You can use a file and go across one way, then the other, and not have to take the filler tubes out..
Get the carb all ground off nice and flat, then screw it down just snug.. not TIGHT, ya know? :shrug:
And yes, some RTV would help ya out a lot, just a fine bead all over both sides of the gasket, just make sure it's not a thick layer, that is going to splatter out everywhere and plug up stuff you don't want it to..