Thanks Adrian>>

I used to be very cautious: we would put the piston at the top of the stroke, tape off the gap to the bore, and wire brush it all off. But one day I was lazy and decided to just vacuum it off with a special shop air powered tool I own (we always used it before to clean the gap after the tape was pulled). And it worked great! It took off all the loose stuff without the possibility of wire brush or cleaning medium or black crud getting into the bore. It didn't take off everything, but the stuff it left you would need to wire brush or blast to get off anyway. And who is going to look once the head is back on?

You need to get it all off, possibly because the compression is so high it pings on hot carbon spots? (850s commonly have this problem.) Completely warm up the engine with the air cleaner removed, then rev it up to about 2,000 RPM, and spray a light mist out of a small hand- held spray bottle of water into the incoming air. The steam will scrub the combustion chamber pretty clean! Don't spray a big stream, water does not compress very well and could cause severe engine damage. I can also imagine doing it too much and washing down the cylinder walls and seizing a piston in the bore.

Make sure you run the engine for at least another 5-10 minutes to get all the moisture out. You DON'T want to shut off a hot motor with water in the combustion chamber!