What are the symptoms when the pulley weights of a scooter are damaged?
4 Answers
Scooter pulley weights that are aged or worn out will cause the engine crankshaft to fail to properly lift the belt pressure plate during rotation. After accelerating, the engine speed increases but the acceleration is too slow, resulting in weak driving performance. More information about pulley weights is as follows: 1. Introduction: Pulley weights are one of the rotating components of a scooter. The pulley weights (also called moving weights, which can move radially) are influenced by the engine speed. As the speed gradually increases, the pulley weights are subjected to outward centrifugal force that overcomes the force of the large spring, moving radially along the sliding groove toward the outer edge of the disc. This increases the force that squeezes the axial movement of the moving disc, enlarges the working radius, and reduces the diameter of the driven disc, thereby changing the transmission ratio. 2. Classification into light pulley weights and heavy pulley weights: Lighter pulley weights provide stronger acceleration, requiring less time to reach a certain speed. However, during movement, the engine speed will be higher than usual. If frequently driving in urban areas, this setup is more fuel-efficient. Heavier pulley weights result in poorer power performance during acceleration, slower acceleration, and a longer time to reach high speed. However, when the pulley weights slide to the end of the pulley disc, the inertia is greater, and the engine speed during operation becomes lower, making it more fuel-efficient during prolonged high-speed driving. The heavier the pulley weights, the greater the centrifugal force generated, which shortens the car's acceleration time. However, the instantaneous torque produced on the crankshaft can be excessive, potentially leading to crankshaft fracture in severe cases. If the pulley weights are lighter, the centrifugal force generated will be smaller, resulting in slower acceleration time for the car.
I've been riding a scooter for over a decade, and when the roller weights go bad, you can really feel something's wrong with the bike. The throttle response becomes extremely sluggish during acceleration, like driving through mud—you twist the throttle, but it takes a full two seconds before any power kicks in. The worst part is when the speed goes above 40 km/h, the engine starts roaring with an unbearably harsh buzzing sound, yet the speed stubbornly refuses to climb. Last time I replaced the roller weights, I found several had worn into polygonal shapes. The mechanic said this causes slippage, resulting not only in slow acceleration but also terrible fuel efficiency. Plus, the transmission case makes loud clanking metal noises, which is especially embarrassing at red lights.
I encountered many cases of variator roller failures when repairing motorcycles before. Simply put, when the transmission system malfunctions, the motorcycle's shifting logic becomes completely disrupted. You'll feel the bike struggles excessively during takeoff, remaining sluggish even at full throttle. During mid-range acceleration, the tachometer needle suddenly surges upward, but the actual speed doesn't increase accordingly, as if the engine were freewheeling. More dangerously, power interruption may occur abruptly during cornering, especially when starting on slopes. If not addressed promptly, such issues can also damage the drive belt and rear clutch.
Last time my Yamaha Ciao had issues, it turned out the pulley weights were worn flat. The bike became extremely sluggish, always getting overtaken by electric scooters when starting from traffic lights. Accelerating to around 30 km/h felt like hitting an invisible wall - no matter how much I twisted the throttle, it wouldn't go faster. Fuel consumption also suddenly skyrocketed; where a full tank used to last 150 km, it barely made 120 km when the problem occurred. The mechanic found all six weights worn unevenly when he opened it up. He said this issue is particularly common on bikes that frequently carry passengers or climb hills.
