take out your spark plugs, use a feeler gauge set [buy a set for around $15, can get bigger better sets for more], and squeeze your plug gap down to 0.80mm, it will be set to 1.0-1.1mm std.
Ask someone to show you how it's done, once your shown its easy, annoy your lawnmower shop or something [anything with a sparkplug], with a plug spanner, feeler gauges, and a spanner set for other bits and pieces, you'd get it done inside an hour or so.