Yes, that's a well-documented characteristic of these engines. The Listeroid 6/1 has about 150 lb flywheels. The Lister Startomatic had flywheels that, by all accounts, were about 300 lbs each. The flicker you see coincides with the compression and power strokes. During the compression stroke, the flywheel slows slightly as energy is transferred from the flywheel to the air charge in the cylinder which is heated by compression. When fuel is injected and ignites, the power accelerates the flywheel slightly. Then the engine essentially coasts for 1 1/2 turns before compressing the next charge of air.
Because the 1800 rpm generator is driven from the large flywheels at a ratio of almost 3:1, whatever speed change there is at the engine flywheel will be multiplied by appx. 3 at the generator head. If you're running a 3600 rpm head, make that 6. That intermittent deceleration and acceleration causes a rapid voltage fluctuation which you see as flicker. Turning heavier flywheels or adding one or more cylinders minimizes that flicker.
As far as affecting other equipment, most power tools, at least the portable ones, have universal motors that are capable of running off very poorly regulated power (think jobsite generator from Costco and long extension cords). Light ballasts can be another story since there are so many varieties, though I've never heard of any problems other than the flicker causing people to complain of headaches. Short answer is: probably no problem. Computers and televisions might prefer to be run off cleaner power, however some folks say computer power supplies are pretty robust these days.
Quinn
