OK if my mower has a little too much compression for my starter to turn is there a way to adjust my briggs 17 hp OHV valves to lessen compression a fraction if so instructions would be appreciated

Hi,
This video shows it well:
YouTube - Lawn Mower Repair Valve Adjustment (http://www.youtube.com/watch?v=NjzX-PUjKmo)
Peace,
Clarke