Like MR305 sead you have to clean it because my bike did the same thing because the guy I bought it from left the bike standing for 6mounths or more so the 2stroke oil seperated from the petrol and made some sticky jelly sh*t in the carb, and chek that you have the right float valve/needle in there. I will even post a pic for you to show you where it is if you don't know where the float valve/needle sits.