Virtually all hit-and-miss engines are of the "open crank" style, that is, there is no enclosed crankcase. The crankshaft, connecting rod, camshaft, gears, governor, etc. are all completely exposed and can be viewed in operation when the engine is running. This makes for a messy environment as oil and sometimes grease are thrown from the engine as well as oil running onto the ground. Another disadvantage is that dirt and dust can get on all moving engine parts, causing excessive wear and engine malfunctions. Frequent cleaning of the engine is therefore required to keep it in proper operating condition.