To clean that problem properly I'd dismantle the whole engine, bearings and all. You never know where metal particles can get into and hide, then reappear to ruin your piston/sleeve when it's running again.
Since it didn't start though you could probably get away with just taking the back plate off and spraying the insides out with brake cleaner or something like that. Then lube it all up again with some wd-40 as long as you're going to start it sometime soon. Don't use wd-40 if you're going to let it set around for awhile.
Good luck to ya, and since it's a novarossi I'd go the first suggested route.