maruader 125 choke?

Ok, our 125 Maruader has the cv carb with cable that goes into the carb on the top left hand side. The carb has just come back from being sonic cleaned due to running problems ie ran ok with choke then died off no matter what we did ,ok so far?. Started up fine and ran great but after 5 mins trip down the road the engine races. The carb cable is shutting off and the fault seams to be the choke .If we undo the 10 mm fixing holding the cable in the carb and remove the cable ,thus leaving a small hole, bike runs fine but revs when you put your finger over the hole ?? any help would be great, many thanks