moneyb.
The carb used in the rincon is called a CV carb, which stands for constant velocity. This carb is an excellent choice for vehicles that are used for a wide choice of altitudes such as utility quads. It would be a poor choice for the sport quads, because they are not designed for performance.
The slide that controls the amount of air and fuel is hampered from opening by the spring that Bigjohn mentions. When the air pressure equalizes from top to bottom of the slide, the slide is then allowed to move up, giving a throttle response. This is why there is a slight hesitation. If the spring tension is lowered by either putting in a weaker spring or clipping the stock one down, it allows the slide to move up quicker for less hesitation. I haven't yet looked at my Rinny's slide, but suspect it is built the same as my XR slide. One of the tricks the XR crowd has learned, is to drill the equalization hole to a larger diameter (5/32") as well as decrease spring tension. This allows the air pressure to equalize faster allowing the slide to move quicker.
I need to look into this someday.
No negative effects that I am aware of, and if you wanted to return it to stock someday, just buy a new spring.
Hope this helps, Paul