Most bikes have the required 5mm gap between the top of the handlebars and the top of the inner fork tube.

If not and depending on the placement of the two side clamping bolts, the handlebars can be raised with the use of a spacer below the bars to achieve this gap.

Also check that your star nut sitting within the inner fork tube is 20mm from the top of the handle bars. If it is not, you can simply thread in a bolt and firmly tap the bolt to push the star nut further down the tube to achieve this.