Just bought a 550 Nighthawk, DOHC I know. I pulled the carbs to give them the old once over and of course there were some screws on the bowls that had there spines a little twisted, as I've yet to not see on a carburetor. I called the Lending Tool Library here in Berkeley, but someone had stolen the impact drivers, classic, and I can't afford to buy a set right now. So I set out to take the tops off and see how gunky these things were. As I started I looked over at a big dent on my truck and remembered this trick of removing dents by freezing them with an upside down air duster. I pulled the tops of the carbs so they wouldn't get banged up. First I leaned with all my weight on the driver to see if I could get it but no luck. I grabbed the air duster from upstairs, turned the can over and froze the screw. I tried to keep the spray right on the head of the screw. It froze and I leaned on it again, no luck. I froze it again, put the philips head back on it, and gave it two light taps with a hammer while turning it and the damn thing popped off with next to no effort! (I had tried the hammer trick previously). I tried the same thing on two more stripped screws and it worked!! Like cutting butter on a hot day.