There's an old carbon removal trick that I'll just mention (not necessarily recommend) that involves running the engine at around 1500-2000 RPM and dribbling a Coke bottle full of HOT water down the carburetor throat a little at a time. It supposedly steam-cleans carbon out of the combustion chambers. I've had mixed results with it, but engines I tore down after the procedure did have pretty clean combustion chambers.
Jerry
As a youngster working in a gas station we were told that slowly pouring a can of STP down the carb while the engine was running was a cure-all for a number of things including carbon removal. I did this a number of times because we got 25 cents for each can we used. In retrospect I think the only we accomplished, besides selling STP, was creating enough smoke that it looked like the whole gas station was on fire.
