That depends. Sometimes your clutch will slip because you have your clutch cable adjusted wrong. Other times your clutch will slip because the friction plates are worn down too much or the steel plates are glazed over. First, check your clutch cable. There should be about 1/8" play in the clutch lever before it starts to disengage the clutch. If there is no play in the clutch lever than you need to loosen the clutch cable a little bit so that it will allow the clutch to fully engage. If there is play in the clutch lever, than you will need to inspect the clutch to determine if it needs replacement.