How do you get the front sprocket off? Is it reverse threaded?
I had the bike in 2nd gear and tried doing lefty loosey and it made the transmission turn while on the rear stand. I tried putting the rear tire down and it acted like it was going to turn the tire against the cement.
Like Mike said, put the front wheel against a wall and have someone step on the rear brake. If that doesn't work I usually put a 2x4 thru the wheel and let it lockup on the swingarm. Reverse it for tightening. I've got an air ratchet that I sometimes take it off with but I like using a torque wrench to put it back on.
"Towards the end of the vid, it looks like she may have had a bafflectomy." - MarylandMike
it takes a little bit of what we call force.... MAKE SURE YOU USE A QUALITY TOOL... if you use the little cheapy sockets you get anywhere you may strip the head.... spend the money get a good craftsman socket or someother HIGH quality brand....