Very hot variator, clutch and clutch cover.

I have a Direct Bikes Scorpion 125cc. Drive belt snapped so I put a new one on (835x20x30).

Since having put it on it works fine for 15 minutes or so then (when it heats up) :

1. When hitting 30 to 40 won't go faster (normally does 60mph to 65mph).

2. The variator, clutch and cover (for the variator and clutch) gets extremely hot. The new drive belt is already cracking and I imagine this is down to the heat. (This did not happen before the belt was changed).

Any ideas?