I disassemble and inspect for shavings and/or small particles. I don't clean the engine, but I do wipe it down with something white, to see if anything shows up. Then I coat everything with after run oil and reassemble. I haven't found anything either, but some people have posted finding metal shavings.
Make sure to watch the orientation of the piston as you disassemble the engine. Pay particular attention to the bottom rim of the piston, as each "side" is different. It has to go back in the same way. For future reference, if you have to remove the conrod, it also has to go in a certain way to allow for proper lubrication of the crank pin.
Nitro Knowledge Base: http://nitrokb.netne.net
My YouTube Channel: http://www.youtube.com/nitrokb -> Lots of on-road nitro & eletric action + some off-road as well
My Flickr Photostream: http://www.flickr.com/photos/nitrokb/
Kyosho V-ONE RRR WC (x2) \ XRAY T2'007 \ Also owned: XRAY NT1 & Mugen MTX-4