Why wont my mini pocket rocket Grand Prix mx3 run?

I purchased my mini pocket rocket about 2 years ago and rode it a few times until it started to leak gas and wouldnt turn on again, its been sitting in my garage ever since. Recently i have decided to take it to a bike shop and get it fixed, the carbunetor has been flushed and cleaned. The motor is clean and is in very good condition, but there is still a few problems. The mini pocket rocket takes forever to turn on after a lot of pulling with the pull start, and when it finally turns on the bike wants to jump up and accelerate without me even touching the throttle, after that i try to ride the bike accelerating slowly and it moves a few yards and then stalls. I really need some help with this problem.