I have a Kohler c18 on a miler welder. It starts up fine but it started shooting sparks and I have no idea why. I replaced the plug wires but it's still doing it. He's is a link to a video I made Of it here
I do not have much experience yet but looking at your clip with windows movie maker we clearly see the sparks starting under the metal plate and not the plug wire.
It seems a wired is under that metal piece and short du to vibration.
look at 4.75 second for the start up to 4.85 second using movie maker or another similar program.
hope this will help you