No, the chain drive is not the only final drive system used on motorcycles. While chain drives are commonly found on motorcycles, there are other types of final drive systems as well. The main alternative to a chain drive is a shaft drive, which uses a driveshaft to transfer power from the engine to the rear wheel. Shaft drives are often found on cruisers, touring bikes, and some sport touring motorcycles. They are known for their durability and low maintenance requirements compared to chain drives.
Another type of final drive system is the belt drive. Belt drives use a reinforced rubber belt to transmit power from the engine to the rear wheel. Belt drives are commonly used on some cruisers and custom motorcycles. They offer similar benefits to shaft drives, such as reduced maintenance and smooth operation, but they may not be as durable in high-performance applications.
Each type of final drive system has its own advantages and disadvantages, and manufacturers choose the one that best suits the intended purpose and design of the motorcycle.