Maybe someone can give me advice about my 2001 YZ426. I had it start missing and popping this summer after riding it for four months. It always starts and idles fine and will run fine for a couple of weeks before the plug goes bad and needs to be changed. It doesn't seam to be a jetting problem because it runs to well, and I follow the YZF rules of not turning the throttle when starting and letting the air filter sit for a couple of days after oiling before riding. I went to a CR7E and this helped but it still doesn't last long enough. I sometime take off to quick after starting and I think this is part of my problem maybe the bike is to cold to burn off excessive fuel.