Jamie: I don't think that's a good idea. I am pretty sure that carb cleaner would slowly leak past the valves, even if they are closed, and into the cylinder wall. It's very "thin" (low cohesive and adhesive properties) and also quite volatile. It'd probably evaporate too fast in an open environment to do any good. And if it didn't, I can imagine it going into the cylinder with dissolved crap, getting on the walls of the cylinder, thinning the oil, getting past the rings and into the crankcase and polluting/thinning that oil...

I think sandblasting with particles too large to go through a closed (nonburnt) valve, and which will burn quickly if not all removed, is the best option.