Talked with KYMCO today, and the stock roller weights are 25 grams. Called EPI just before, and they recommend going 5 grams lighter on roller weights. Guys from EPI are great. They didn't see anything for the mongoose 300, and after digging around they found the components are the same as the MXU 500. This is what the guy said from EPI.
Now I know what components to order for the clutch, I wonder how much improvement a HMF exhaust and a K&N filter will do.