Low end troubles

[takadi]

So I'm having some troubles on the low end. 150 cc chinese bike. Starts fine, idles horribly. Struggles to idle and has spurts of high idle here and there. When I open the throttle the scooter stalls and shuts off. However, when I leave it on for a while and warm it up, the idle starts to pick up and then it idles beautifully, almost too strongly. The problem at the low end still remains though. It has a delay - open up the throttle slightly and nothing happens for half a second, then the rpms pick up. Getting past the low RPMs on wider open throttles everything is perfect.