There are two cases to be considered here both the carb and the clutch could be culprits here. Let me explain.
If the engine warm and is at the normal operating temp and you floor it and no acceleration that means the culprit could be clutch.
If the engine is not warm enough and it has only been about 5-10 minutes then it is the carb, there is a specific term to explain this phenomenon. In this case you floor the throttle and poor response and if you go easy on the throttle and you get the corresponding acceleration.
Before you confirm it is the clutch ride it for about good 30 minutes and then roll the throttle like mad and see which case it falls under.
but don't forget to check the adjustment to the clutch make the cable little tighter and see if it makes any difference, this is a simple thing to do and hurts nothing, you can revert it back real easy.
