When performing engine overhaul, it is necessary to change the main and big-end bearings and keep the old ones as they may be used to give information about the condition of the engine. Carrying failure can be in the form of insufficient lubrication, dirt ingestion, engine overloading, or corrosion and what is essential is to correct the cause and not to repeat the failure before it occurs again. When checking bearing shells, take them out of their place and spread them in a clean place so that they can be easily matched with the crankshaft journal without touching its internal surfaces to prevent scratches. When assembling the engine, foreign particles might enter it or via filters and ventilation systems and may become embedded in the bearing material, or result in scoring. Complete cleaning of the parts and frequent changing of the oil are crucial in prevention. Excessive heat, overloading, oil leakage or blocked passages can result into severe damage of lubrication breakdown. Driving styles (i.e. full throttle low speed use) may also harm bearing life by resulting in fatigue failure. Mini journeys may cause corrosion because of lack of heat whereas improper installation may cause oil starvation or high spots which cause failure. The reassembly should be done carefully not to contaminate the bearing surfaces. Main, big-end bearings are offered as standard and undersized to accept reground crankshafts and running clearances require checking when installing new bearings.