The new Sirio EVO3 does not suffer from that problem. I would say that it is very reliable, if you consider that I replaced the two bearings and the conrod/pin after 12 lt (6 races with the practise on Saturday) and the engine performed really well until then. Of course I was diassembling the engine for cleaning and inspection after every meeting. After the replacement, the engine was better than before, cause the piston was really in his best shape for performance.
I am very satisfied and I would recommend this engine.