I've got a strange sound when idling. Its coming from the cylinder, i think. I've changed the piston+ring+bearing, crankshaft+bearing, main bearings, and just renovated the cylinder. The sound disappears when i rev it just a little bit over idle. But comes back when the rpm lowers again. I'm running 98 fuel, with 3% oil in it. The engine runs really great, its just the sound thats concerning me. What can this be, and what should i do to get it to stop? Thanks!