Check/renew the gasket at the carb to engine flange.Chances are it's shot.
caine
July 2008
This might help
Look on the side of the carboretta they should be a flat head screw to control the revs try turning it clockwise if too high or anti clock wise if too low.
if all else fails replace the air filter because that some time can effect the running of any mortor
hope it help