We all know the American V-Twin motorcycle engine is designed and engineered for maximum performance based on the air-cooled principle. But in the process of modifying one of these motors, for either more power or for show quality looks, the theory of proper air-cooling can be thrown completely out of whack.
There are two ways the American V-Twin air-cooled motors stay cool and that is by convection and radiation.
These methods happen when the heat produced from an air cooled motor is removed by the movement or circulation of air over the cooling fins of the heads and cylinders. This process gives the “hot” parts of the engine an opportunity to lose or dissipate the produced Powdercoating heat quickly.
When you are sitting still, like being stuck in traffic, the ability to keep your engine from overheating obviously becomes impacted due to stagnant airflow. All that heat buildup needs to go somewhere and will begin to spread into other parts of your bike such as the engine cases, transmission, primary components, etc. and in some cases your pants and finally into the physical space you’re sitting in!
Proper cooling techniques were implemented when theses engines were designed and measures were taken to keep them at an acceptable running temperature such as putting lots of cooling fins on the heads and cylinders. You may have noticed that the fins on a stock engine will have a rough finish to them and this is done for a reason. All those little pores in the metal help in getting rid of the heat. Even the black (finish) wrinkle paint is there to help get rid of as much heat as it is to look good.
A couple of the worst things you can do, as far as trapping heat in your motor, is to either chrome or powder coat cylinder barrels and heads or remove some of the cooling fins on them. When this sort of procedure is done to an engine, it really handicaps its ability to shed heat resulting in much higher running temperatures due to the heat being trapped inside with no way to properly relieve it.
Think about it. You know your motorcycle is generating heat while it’s running. And you know that heat dilutes the amount of potential power an engine can produce. So why would anyone do something to a motorcycle that would keep heat intentionally trapped inside the engine?
On air-cooled motors, besides the oil and maybe some other cooling support components, AIR is the only place the produced heat has to go. And if you have an engine that you’ve added performance upgrades to so it will produce more power, the motor will generate even more heat.
The bottom line is if you’ve made some sort of modification to your engine such as chroming or powdercoating the heads and barrels, or removed some cooling fins, you’ve seriously impaired the engineered balance of the air-cooled engine principles. By causing heat to stay trapped inside of your motor, you are definitely going to shorten its life cycle along with possible damage to other components of the motorcycles drive train. Chrome and powder coating look great, but give a little thought to the potential effect on the performance and wear of the internal parts of your motorcycle.