Piaggio zip help needed or anyone with mechanical skills ;)

Someone please help its starting to do my head in now. When it's cold and I pull back to full throttle its pulls away fine and fast but after a 10 min ride it pulls away slow and take ages for the revs to pick up and the only reason it even moves when it does that is the rollers kick in once the rollers kick in its runs fine all the way to 60mph but as soon as you stop and go to pull away it does it again? But its fine when you just start the bike. And if you leave it ticking over for a bit and then pull away it's fine but if you rev it and then try to pull away it goes slow again? Basicly I have to come to a stop let the revs drop to ticover and not do anything until I have to pull away!! It's fine to ride but when I've got to pull away into fast traffic and it does like 5 mph for like 2 mins it's dangerous so please help me

 

Piston rings are fine and the compression is fine too. And I put 2k clutch springs in it so they are quite new?

 

Ye it's your clutch springs you need stiffer 1s mine did do the same n the reason it pulls away fine wen u first start it is because your clutch slips wen cold so you can hit your power band at stand still so pulling away Is fine but wen clutch is warm it grips more so it's not reving high anuf to hit the power band so pull away is poor so get stiffer clutch springs nd itl b fine

 

2000 rpm clutch springs are in it at the moment? They don't get much better than that?