hi there johnando and a warm welcome could be a few things really , cable too tight ? idle screw not correct ? too lean at idle maybe ? gov' spring stretched ?
resident reel mower dude BB will assist you well and fast with your machines i'm sure . but a few photo's will help all to assist you mate and hope you get all the help you need here , just help us help you with a few pic's .
could be a few things really , cable too tight ? idle screw not correct ? too lean at idle maybe ? gov' spring stretched ? 
Dave 
