Crankshaft bearings for DIO 18/27 (manufacturer TATA). They secure the crankshaft in the crankcase and let it rotate at high rpm.
Replace them if the engine hums and vibrates, if the shaft has noticeable play, or during an engine overhaul. Replace the bearings as a set together with the oil seals, otherwise the new bearing will quickly fail. After installation, check that the shaft rotates without binding and without noticeable play.
