I've been looking into the STS engines myself. I've been reading good things about them and they can be had for very LOW prices on ebay. As far as parts go, www.racernine.com is a dealer and the prices aren't bad. A piston/sleeve set us $50, shipped in the CONUS. That would just about make it worth doing an overhaul on a $110 engine. Of course, the conrod is another $28 though.

Now that I think about it, for $110 or so for an engine, when it dies, I'd just get another engine.

What I was more interested in was the .21 engines. I wonder how those run.