I took the updraft carb apart and the main jet threads are a little messed up and can not get the new one back in, What size threader do i need to rethread where the main jet go's into the carb?
Take the jet to the hardware store and match up with a tap.
There are two uncommon threads used on a Briggs Flo-Jet:
5/16 - 32
1/4 - 32
One is for threading nozzle to body. other is for threading needle to body.