If the carb slides aren't installed properly they won't work properly.
They work off of air flow, and if they aren't seated properly they won't work, and you won't have any throttle. It will be like a car when you open the throttle there won't be anything there, and it will bog and not accelerate.
They are pretty easily fixed, but you have to take the tops off to do it.
And if you have the stock airbox, it will be a pain, You will have to remove the carbs.
The way I check mine is to blow in the port in the tops of the carb inlets.
You can also check them with the carbs on the bike, but you have to be careful.
If you have access to an air nozzle, GENTLY blow air in the ports at the tops of the carbs, and watch the action of the slides. If they are sluggish or won't open then you either have a leak, or the slides are sticking.