have just rebuilt my gk73a after 3 yrs, passed mot with flying colours. the throttle cable snapped 3 days later and has been replaced, havent touched anything else. now when i start it revs the guts out of itself at about 8k rpm. have adjusted the throttle cable so there is slack, and done idle screw all way in and then out 1 1/2 turns but it still keeps doing the same, any ideas. it ran well before cable broke

regards mark

What do you mean by idle screw?.
If it's the one on a short cable under the frame spar then that shouldn't be screwed all the way in at all.
Just unscrew it untill the revs come down.
1.5 turns out sounds like the pilot air screw settings of the carbs.