Just
Quit
Idling

The problem will go away as soon as you start using the engine the way it was designed to be run. Until then, keep a spare set of plugs handy and take the fouled ones to somebody with a bead blaster. I went to the race track with 3 or 4 sets of clean plugs every week, which we used for checking the carb mixture during practice. After the race, I just cleaned 'em all up and re-used them the next week.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!