A different clutch.
Those arms are made of balsa wood
Maybe you could adapt a Ciao's clutch idk but idk if they're any better but I think so.
And honestly if you're trying to get all big dick power on this kinetic,
Modify the case half to add reeds and then put a big boy carb on it, like a 21-24mm carb.
Then you'll have some big power.
Though it's likely once the engine has that power it very well might eat itself (destroyed crank, rear gearbox, etc)
I don't know if Vespa Ciao aftermarket cranks swap in.