which carb doe sit have on it?
it's possible that you have the slide in the carb wrong.
There are 2 slots in the slide, a long one and a short one.
The short slot should be on the left where the idle screw is at.
if the long slot is on the left side, there won't be anything for the idle screw to seat against. The long slot gets lined up with a little pin that's cast into the side of the carb on the inside.
BUT, normally if the slide is in wrong, you will have no throttle response and the slide will be bound up in the carb.
if the slide is in right, you may have to remove the float bowl and make sure that the main jet is still screwed in.
sometimes the main jet will loosen up and fall out into the float bowl.
if there is no main jet, it will not idle and it will be getting way too much gas when you ride it...normally the engine will run, but not very well, and it will be way too rich.