ORIGINAL: controlliner
If the engine is running well, don't do anything. If carbon builds up too much it will be ejected out the exhaust. The only time I have been concerned is in a ringed engine when the ring or rings were stuck. Then I would take the piston out and soak the piston crown in Varsol.
Varsol? I have not heard of that since the late seventies; used to buy it in my own jug from the hardware store for 75 cents a gallon. Used it for everything (well, almost everything), including paint thinner, brush cleaner, parts cleaner, kerosene lamp fuel, and charcoal lighter fluid. I guess it is marketed in cans now for 12-15 dollars a gallon. Good old days!?!
I still have my Fox .35 and K&B .29 Greenhead CL engines from the fifties when I bought them new, big bucks then.
Cheers, and congrats on the hockey win.
Sincerely, Richard