You don't have the throttle slide lined up in the carburetor properly....unscrew the top of the carburetor and pull the throttle slide out, look at the slide itself...it can only go in one way. there will be a narrow slot on one side and a short,wide angled slot on the other. the short, wide slot must line up with the idle adjustment screw on the outside of the carburetor and the narrow slot must line up with the cast in peg inside the slide bore. If you do not do this the slide will not hit bottom and it will be held in about the 3/4 throttle position at all times...
Don't worry...just run watcha brung...