How effective is Staybil? I have heard both good and bad about using it - the bad is fouled plugs mainly. Not a giant problem in a car, but something of a hassle in a generator with it's lower power and inability to burn off deposits. I use Jiahua (a gallon or so may have accidentally fallen into the kit bag at one time or another
) but am getting low again.
As far as covers go, my instinct would be don't. Our gennie is out in the shed. It slides neatly into a box made of 8 ply marine grade, joints sealed with silicone and the whole given a good treatment inside and out with marine grade latex paint. The open end is double, with weatherstripping to give a good seal when the front goes on and has two 15mm vent holes with a double layer of mosquito net glued and siliconed on the inside of it to prevent vapour build up on hot days. The tail end has the same, but about 6 inches from the base, to allow good cross ventilation.
The baseboard itself extends out beyond the box and is beveled to allow the gennie to easily be removed or put back. A small box attached to the left hand exterior side holds spare plugs, points, two regulators, a spark plug wrench, small wire brush, feeler guage, two screwdrivers and the allen wrench you need to get the cover off! Those are all vacuum sealed in heavy grade plastic, to prevent rust.
There was some room between the generator and the top of the box, so a spare copy of the manual was laminated and is in a custom pocket there, where it is handy.
No dust. No bugs nesting and causing havoc. Total cost - one sheet of marine ply, and paint and silicone you already have in the tool shed.
Need the gennie? Pull it out of the box (remind me to put some wheels on it, not getting any younger), hook it up to a line leading to the house (which also runs the external freezer and shed light, it's just swap the plug from one socket to another) and fire it up. The shed is well ventilated, since we dry hams and salami in there, but there is a monoxide alarm, just in case.