Those square bodies are the big deal now-a-days!.
Good trick with the CO2, Last time I did the locked out w/engine running "trick" I used a pair of vice grips and pinched shut the rubber fuel line from the tank.
Things I learned _not_ to do,
Disconnect battery (burns up the points)
Pull coil high tension lead (OUCH!)
Old rag over carb. (pull carb later to remove old rag bits from manifold)