1. Cost: Cam chains with plastic tension pads are a less expensive option than gears. This is one of the most significant factors because, since Harley builds large quantities of production motorcycles, this directly affects their bottom line. With plastic tensioner cams and less expensive manufacturing methods than gears, Harley can pass those savings on to consumers.
2. Weight: Cam chains with plastic tension pads are lighter weight than gears. While many argue that the difference is negligible, this does indeed play into the overall weight of the bike and the bike's center of gravity. This is another significant design reason for Harley's choice of cams.
3. Noise: Cam chains with plastic tension pads are quieter than gears, reducing noise pollution. Harley engines are known to "sing," which is the distinctive sound of the engine's cam chains rattling. Many motorcycle enthusiasts enjoy this sound and feel it adds to the riding experience.
4. Design Complexity and Simplicity: Cam chains with plastic tension pads are simpler in design than gears, making them easier to maintain and repair. Due to the reduced number of moving parts compared to a cam gear drive system, fewer things can go wrong with a cam chain drive. This translates into less servicing for the rider.
While aftermarket cam gear drives are available for Harley-Davidson engines, they offer no real advantage over the stock cam chain system. In fact, most aftermarket suppliers' cam gear drives can create more problems and increase maintenance complexity with their additional moving parts.
