KDX 220's are notorious for broken piston skirts. I would recommend doing a search for this topic as it has been discussed several times before.
It is advised to definately use the Wiseco piston and not to hone the cylinder instead, as mentioned, use a Scotch Brite pad with some degreaser, I use the product called Simple Green, works good and is biodegradable. All you want to do is to remove the gum and tarnish on the cyclinder walls. The Scotchbrite pad will "scuff" the cylinder enough for proper ring/piston breakin. Kawasakis have a very thin nickle plated coating on their cylinders.
I just did a top-end on my KDX 200 and used, and did exactly this. Followed proper breakin' :aj: and all is well. Started 3rd kick :flame: