When you consider the time and cost of parts rebuilding it, you could find a used one for less. We have found this out working on carts at the local golf course. New ones will set you back $150-$350, depending on the source. You will find most likely that the clutch weights and ramp buttons are hanging in grooves that are worn in the faces of the sheave in side. If this is the case you have to replace or remachine the sliding surface on the sheaves inner side. You will be wise to find a book on it. There are springs compressed under snap rings on most golf cart clutches. Sometimes when you pull them off the engine shaft you will find they are filled with dust, dirt and trash that will not let them slide in or out. Cleaning them may get you back going for a while.
On the 2 cycle E-z Go engines, it is a good idea to change the crankshaft oil seal while the clutch is off.
Try looking on various golf cart forums for parts and advice. One site that is good is this one. Buggies Gone Wild
When you reinstall a clutch on these engines, clean the inner and outer tapers off good and lightly oil both sides with some very light oil and DO NOT USE ANTISIEZE OR GREASE ON THE TAPER!