Some interesting things to note:
Note the spark event and how long it actually occurs from start to finish.  Also watch around the perimeter of the intake valve when the combustion starts, this is where the mixture is not optimal and is evidenced by a 'dirty' burn. This could be caused by some of the fuel not fully changing from a liquid to a gas during the compression stroke.  Finally look at the relief on the underside of the intake valve.  Note how you can see a wave or thermal front that propigates across the valve face just before the valve closes and again just before the piston reaches top dead center.