Hellgate
Wizard
+ 4 on the impact gun for the sprocket. It will hit it so hard and fast it will zing right off.
you could pop it in gear also. Im sure you knew that. If you dont have an impact gun then put your 1/2 drive breaker bar on it and apply pressure just enough to take the slack out and hit the end of the breaker bar with intent to loosen it faster than the crank has a chance to rotate..
I tried the breaker bar and bought the impact wrench. I even had a 3 foot cheater bar on it, and a pipe through the wheel and swingarm. The IW, zap! It was off.