Kymco Super 9 responds to the accelerator but starts late?

Hi everyone, I recently bought a Kymco Super 9. When I accelerate, the scooter responds, but it doesn't move immediately. Only when I accelerate hard/for a long time does it move (and then it's really fast). Does anyone know what's wrong? The previous owner had played around with it a bit (Malossi Multivar, Malossi clutch…