Engine oil should be maintained at the appropriate level, but it is not necessary for it to be always completely full. The oil level in an engine should typically fall within the designated operating range as specified by the manufacturer. This range is usually indicated on the dipstick or oil level sight glass.
Overfilling the engine with oil can actually be detrimental to its operation. When the oil level is too high, it can cause the crankshaft and connecting rods to come into contact with the oil, resulting in foaming or aeration. This can lead to reduced lubrication effectiveness and potentially cause damage to engine components.
Conversely, if the oil level is too low, it can lead to insufficient lubrication, increased friction, and accelerated wear of engine parts. It's important to regularly check the oil level and add or drain oil as necessary to keep it within the recommended range.
Refer to your motorcycle's owner's manual for specific instructions on checking and maintaining the oil level. Following the manufacturer's guidelines will help ensure optimal engine performance and longevity.