cast iron or cast alloy can be tig welded...it wont be back to 100% but it will do the job fine...unless he sumhow does the same thing then she's brake....p.s i'm a welder
buy a new fuel line and a good fuel filter..i know it sounds liek it has nothing to do with the carby problems but i had a similar problem to you and i put a new fuel line on and it goes fine now, the old one was kinked and not enough fuel could get through and therefore altered the way it runs.
cheers