What Causes the Clicking Sound in the Scooter's Transmission Box?
3 Answers
Scooter gearbox noise could be due to damaged transmission gears, bearings, or problematic gear oil. Sometimes, poor brake shoe blocks might also cause abnormal sounds. Additionally, check for issues with the pulley, as faults here can transmit noise to the gearbox, making it sound like the gearbox is the source. Here's some extended information: Principle: Scooters use continuously variable transmission (CVT), where the principle involves the overrunning clutch driving the transmission box, ultimately transferring power to the rear wheel drive. Inside the transmission box, a small driving gear rotates a larger driven gear via a belt. Hazards: If gear incremental clearance or meshing clearance is too large, or the belt is too loose, it can cause gear displacement or poor engagement clearance during acceleration, leading to abnormal sounds. Similarly, when the throttle is released, the engine speed drops, altering the transmission ratio, and the belt and gear engagement changes, which can also result in abnormal sounds.
A couple of days ago, my neighbor's scooter had the same issue - you could hear the transmission case rattling from far away. When I helped him take it apart, sure enough, the front variator pulley's track was worn with grooves, causing the rollers to bounce and knock inside. Some bikes have issues where the belt gets stretched and flaps against the housing, sounding like drumbeats. If the rear clutch shoes develop sharp edges, they'll make clicking noises during takeoff. Oh, and last time my cousin's bike had scattered bearings in the clutch bell, making it sound like shaking glass marbles when riding. Never ignore such abnormal noises - get it checked at a shop immediately. Small issues can turn into major repairs if neglected, and that's just not worth it.
I've encountered this issue multiple times. Transmission case noise is most likely caused by problems in the CVT system. The most common culprit is worn or deformed roller weights - when three weights become irregularly shaped, they'll make a rattling sound. If the rear clutch shoe springs weaken and fail to engage properly, or if the clutch bell inner wall gets grooved, it'll produce a clunking noise. Here's a key detail: if the noise only occurs during the first few minutes after cold startup, it's often due to sludge buildup in the transmission case causing the belt to slap against it. If you've installed low-quality aftermarket CVT kits, the larger component gaps will amplify the noise. I recommend focusing inspection on these areas - disassembling the transmission case is actually quite straightforward.
