i have 5 of these blowers, they usually are good to me, i bought this one a year and a half ago. It only takes a few minutes after i put a new plug in until it starts to run rough. I take the plug out and its all burnt looking, even the top of the piston looks like it has some burnt white ash. I cant figure this one out, any help would be greatly appreciated. Btw, i have a new air filter, fuel filter and the spark arrestor is out.