My clutch on my 1980 XR80 is slipping. It slips in every gear mainly in 5th and when I shift too. If I am riding over bumps, say potholes, it slips really bad and it takes a long time to accelerate. If I give it full throttle it will slowly rev up and then they will shoot up as if I disengaged the clutch and the bike will stay at the same speed. Do I need to replace the entire clutch or just the springs or plates or basket? How much will this cost?