Scooter Problems

From St Annes, 1 post

I have a 2002 yamaha XQ125 Maxster. The problem is a loss of power - it will not exceed 40mph and this drops to 20mph on even slight hills.
I have installed a new drive belt, new clutch, new rollers in the variator, new battery, new air-filter and new spark plug. I have checked and adjusted the valve clearances.
The scooter starts OK but doesn't have any power. It's only done 7500 miles and has had regular servicing, including oil changes at every 750 miles. There is plenty of compression - it just won't rev or pull like it used to. I've tried running it without the air filter but this makes not one bit of difference. The exhaust is the original but is solid and the scooter has hust passed it's MOT.
I'm a bit stumped I must admit. I wonder if it might be the electric choke sticking ?
Any help would be most appreciated.