The Harley-Davidson Milwaukee-Eight 107 engine is not fully water-cooled; only the cylinder heads are water-cooled, while the rest of the engine is air-cooled. This design is often referred to as “Twin-Cooled” by Harley-Davidson, and the primary motivation behind this setup is to enhance rider comfort by reducing heat in the cockpit area, rather than for motor cooling.
Understanding the Harley-Davidson Milwaukee-Eight 107 Engine
The Harley-Davidson Milwaukee-Eight 107 engine is a powerful and advanced powerplant that features the following specifications:
| Specification | Value |
|---|---|
| Bore | 3.937 in (99.98 mm) |
| Stroke | 4.375 in (111.12 mm) |
| Displacement | 107 cu in (1,745 cc) |
| Compression Ratio | 10.0:1 |
| Engine Torque | 111.4 ft-lb (151 Nm) at 3,250 rpm |
| Lean Angle, Right | 32 degrees |
| Lean Angle, Left | 31 degrees |
| Fuel Economy | Combined City/Hwy 45 mpg (5.2 L/100 km) |
This engine is used in several Harley-Davidson models, including the Ultra Limited, Ultra Limited Low, Road Glide® Ultra, and Tri Glide® Ultra.
The “Twin-Cooled” Design
The Harley-Davidson Milwaukee-Eight 107 engine is not fully water-cooled, but rather features a “Twin-Cooled” design. In this setup, only the cylinder heads are water-cooled, while the rest of the engine is air-cooled.
The water-cooling system in the cylinder heads helps to reduce the heat in the cockpit area, which can enhance rider comfort, especially during long rides or in hot weather conditions. This design choice was made by Harley-Davidson to prioritize rider comfort over pure engine cooling performance.
Comparing Water-Cooled and Air-Cooled Engines
When comparing water-cooled and air-cooled Harley-Davidson Milwaukee-Eight engines, there are a few key points to consider:
-
Airflow Enhancements: There are various products available that can enhance the airflow around the cylinders of air-cooled bikes, potentially lowering their operating temperature. This can help to mitigate the inherent limitations of an air-cooled design.
-
Heat Source: The primary source of heat in a motorcycle engine is the combustion process, not the engine oil. As a result, the impact of motor oil on cooling the engine is relatively minimal.
-
Synthetic Oil: Synthetic oils, such as Amsoil, can maintain their lubricating properties at higher temperatures, allowing the engine to run hotter without losing lubrication. However, this does not necessarily make the bike run cooler overall.
Conclusion
In summary, the Harley-Davidson Milwaukee-Eight 107 engine is not fully water-cooled, but rather features a “Twin-Cooled” design where only the cylinder heads are water-cooled, while the rest of the engine is air-cooled. This design choice was made by Harley-Davidson to enhance rider comfort by reducing heat in the cockpit area, rather than for pure engine cooling performance.
When comparing water-cooled and air-cooled Harley-Davidson Milwaukee-Eight engines, there are various products and techniques available to help manage the heat in air-cooled engines, but the primary source of heat is the combustion process, not the engine oil. Synthetic oils can help maintain lubrication at higher temperatures, but they do not necessarily make the bike run cooler overall.
References:
– Harley-Davidson Milwaukee-Eight Engine on Wikipedia
– Which M8’s are Water Cooled or Oil Cooled?
– All-New Harley-Davidson Milwaukee-Eight
– 2017 Harley-Davidson Milwaukee-Eight 107 Released
– Harley-Davidson Milwaukee-Eight 107 Engine Overview