The BMX stem plays a big part
The purpose of the stem on a freestyle BMX is to attach the bar to the fork. It is in the stem the compression is made.
The freestyle BMX stem plays a great factor in how the front end is going to feel. The primary difference between the freestyle BMX stems are the length and the increase of height. Height and length are both factors that can affect how fast the balance point appear on the bicycle. A short stem will give a more responsive front on the BMX, where a long stem will give a more slow and controlled front. The freestyle BMX stem determines how far away from your chest the bar is. A short stem combined with a fork with a short wheel offset makes it easy to get up on the front wheel.
Do you need a top load or a front load stem?
There are two ways the bar can be mounted on the stem, top load mounting and front load mounting. On a frontload stem the bar is mounted on the front of the stem. A frontload stem is often preferred by the taller riders, since it places the bar further away from the rider.
On a top load stem, the bar is mounted on the top of the stem. The top load stem is taller than the front load stem. A top load stem is recommended, if you prefer to ride with a taller bar.
Take note: Be be sure that the stem you are looking for is the same size as your handlebar.