CT- have you tried a different plug wire at all? Sometimes those just crap out...
Jumpa(and all)- For those of us not lucky enough to have the sprocket seat nicely on the hub(*shakes fist at the lucky ones*
). When the sprocket's still loose, stuff short pieces of fuel line, or cigarette butts, or whatever fits evenly around the hub. That'll get the sprocket closer to "true" for final tightening. Plus it's easier to keep an eye on it with something there to gauge by than just the gap.
I've just been working around the house(*shakes fist at roofing tar*) and prepping the winter beater for when the salt starts flying. No way I'm taking the 29er out in that, with the J-shaft and all the chrome it'd look like crap inside a week.