I done changed the plugs and air filter after 8000 miles on the bike. Noticed my MPG's dropped to avg around 43mpg and before I was getting about 49mpg average. I notice the idle might be a tad rough, and I mean just slightly "rumbley" instead of "humming". Anyway I'd expect the mpgs to improve after this procedure. Am I running rich? How can I adjust the fuel/air mixture?