Toki .27....I've never heard of that brand and that's a pretty oddball displacement. I think your best bet is to scrap it and buy a new engine from a reputable brand, such as Losi, OS, HPI, and then break it in and tune it properly. As for obtaining a piston and sleeve for your existing engine your best bet would be to try to find Toki's website, but that's no guarantee they'll offer parts. The place you bought it should stock them as well, provided they're reputable and the parts are still in production.