nrg
You can use a putty knife to scrape off the larger carbon off the head, top of the piston and valves but when you get down to the lighter carbon, I use a scotchbrite (green) scouring pad. It's mildly abrasive. If you are careful you should be able to leave virtually no marks. But a few tiny marks won't do you any harm as long as it's not on the valve seat or cylinder wall.
sometimes I use a little varsol on the scouring pad and that takes it off also. Just don't use the varsol near any open flames.
snoman
You can use a putty knife to scrape off the larger carbon off the head, top of the piston and valves but when you get down to the lighter carbon, I use a scotchbrite (green) scouring pad. It's mildly abrasive. If you are careful you should be able to leave virtually no marks. But a few tiny marks won't do you any harm as long as it's not on the valve seat or cylinder wall.
sometimes I use a little varsol on the scouring pad and that takes it off also. Just don't use the varsol near any open flames.
snoman