Clutch problems Vespa PK50 XL2

Hi everybody,

I'm Simon and this is my first time on the forum.

I have a problem with the clutch of my Vespa PK50 XL2.

When I use a new clutch pressure plate, the clutch is dragging a little bit. But when I try the old clutch pressure plate, the clutch isn't engaged. I have a new clutch cover and a new clutch (a Ferrodo one). Could anyone help who had the same or a similar problem. 

A big thank you in advance [:D]
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Simon.
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