Honda GX110?

Hi
Honda GX110 will start and tickover but cannot get it to power up. I have taken the carb off and cannot see any issues, fuel is flowing as I have taken off the drain cap. Have replaced spark plug with no improvement. Did try to take out the jet but it didnt seem to want to fully remove easily and I didnt want to break it. Would you suggest a new carb, as can get on ebay for about £15 although not honda original part. Any suggestions, as this is on my sons go kart and he is really upset it wont run.
Thanks