So all 3 lights are on? Assuming the tach/hour meter is battery-powered like this one
http://www.electricgeneratorsdirect....-4C/p1193.html
I don't see how it could cause all three lights to light. I also don't know why it would say 3000 RPM and then 12000 RPM with no change in motor speed. Something is weird, but I have no idea what. Can you temporarily unwrap the tachometer sensor wire from around the spark plug wire, leave it hanging into space, and see if anything is different? It is at least possible that this wire is acting as an antenna, and radiating the spark plug impulses (very high voltage) into the ground connection, which could light the ground-to-neutral and ground-to-hot lights that are normally off. I don't have much faith in that thought, but I have no other.
Remember that two lit lights is correct for a household outlet or a campground power post outlet. But for an outlet on a generator, only one light should light. Two lights is NOT correct on a generator outlet.
Bill