liquid 


motorcycles have a radiator (similar to the radiator on a car)
 which is the primary way their heat is dispersed. Coolant is constantly
circulated between this radiator and the cylinders when the engine is running.
 While most off-road motorcycles have no radiator fan
 and rely on air flowing over the radiators from the forward motion of
the motorcycle, many road motorcycles have a small fan attached
 to the radiator which is controlled by a thermostat.
 Some off-road motorcycles are liquid cooled and anti-dirt protection
 is attached to the radiator. The cooling effect of this fan
is enough to prevent the engine overheating in most conditions,
 so liquid-cooled bikes are safe to use in a city, where traffic may frequently
 be at a standstill.
Emissions regulations and the market demand for maximum power
 are driving the motorcycle industry to liquid-cooling for most motorcycles.
 Even Harley-Davidson, a strong advocate of air-cooled motors,
has begun producing a Revolution liquid-cooled engine.

Air

Most air cooled motorcycles take advantage of air blowing past the cylinder and cylinder head while in motion to disperse heat. Frequent, sustained stationary periods may cause over-heating. Some models (mostly scooters) are equipped with fans that force the air to go past the cylinder block, which solves the problem of city driving. The cylinders on air cooled bikes are designed with fins (heat sinks) to aid in this process. Air cooled bikes are cheaper, simpler and lighter than their water-cooled counterparts

Oil

Some manufacturers use a hybrid cooling method where engine oil is circulated between the engine case and a small radiator. Here the oil doubles as cooling liquid, prompting the name "oil-cooling." Suzuki has produced many "oil-cooled" motorcycles. Modern BMW R-series flat-twin motorcycles, such as the R1150GS, use air and oil cooling. Polaris's Victory motorcycles use oil/air cooling exclusively.