Loosen the goose-neck (adjustable quill stem) with a 6 mm Allen wrench.

After loosening the goose-neck (adjustable quill stem), it still may be stiff. Hold the wheel from turning and twist the handlebars from side to side.

If quill stem is still stuck then place 6 mm Allen wrench firmly into bolt and tap with a mallet.

Position the handlebars to your preferred height. Make sure not to pull cable and housing to tight. I could adversely effect shifting and braking performance.

Make sure you don't raise quill stem above minimum insert line.