I was gonna say, "What they said" until WD-40 came up. We had a guy on here several years ago suggesting putting some kind of grease on the clutch! I ignored that suggestion, too! I don't know. It may be the best thing yet. All I know is that WD-40 gets gummy and sticky when it sets, dries, whatever.
We have both GTi300 and DT300i and both have identical clutches. They are in design and character the same as the Agility 50 and the Yager 200i. Sand off the glaze, sand inside the bell and clean out the dust, use aggressive starts rather than "feathering." Repeat when necessary.
Shows how much the dealer techs know replacing these thing when they get grabby-crabby. Sell lotsa clutches. Not their money....