What is the reason for the unpleasant sound change in USR125?

[OliveAnn]

It may be the sound caused by the thermal expansion of the internal structure of the exhaust pipe. Below is an introduction to the Haojue USR125: Scooter: The USR125 has a strong sci-fi feel, with a unique style that stands out on its own. The USR125 is like the "DR160" among Haojue scooters, and its appearance has broken the impression people had of Haojue's previous scooters. Appearance: Multiple LED lights, a full LCD instrument panel, aluminum alloy folding footrests, a USB charging port, and the application of matte paint throughout the vehicle make the USR125 more luxurious compared to other models in the same class. Its price is on par with joint-venture vehicles in the same class, making it the highest-priced 125cc product under Haojue and confirming the USR125's flagship status. Comprehensive tests show that the Haojue USR125 is fully capable of competing head-to-head with current joint-venture vehicles in the same class in China.

[LaMiranda]

I've been driving my USR125 for several years, and recently the sound has become particularly rough, dragging and unpleasant to hear. I think the most common issue is carbon buildup in the engine, possibly due to poor fuel quality or not cleaning the spark plugs regularly, leading to incomplete combustion and unstable idle, which causes strange noises. The exhaust system might also have leaks, with a damaged muffler or aging pipes, making the sound louder and noisier. Additionally, if the fan belt is loose, the squealing becomes even worse. I've encountered similar situations before—if left unchecked, engine wear will worsen, and repair costs will double. Regular maintenance, such as changing the oil every 5,000 kilometers and checking the spark plugs, can prevent these issues. When the sound seems off, don’t hesitate—take it to a professional repair shop immediately for a diagnostic scan. Otherwise, you risk sudden stalling or breaking down on the road, which would be a much bigger hassle.

[StephanieFitz]

As an experienced DIY car enthusiast, when my USR125 starts sounding rough, my first suspicion is an ignition system issue. Improper spark plug gap or aging ignition coils can cause misfires and disrupt engine rhythm. Fuel delivery is another concern - clogged injectors or a weak fuel pump leading to overly lean/rich mixtures will make the engine sound coarse. Exhaust leaks amplify metallic vibration noises. Worn fan bearings often produce rattling sounds. The key is using an OBD scanner to read trouble codes and pinpoint issues - never just guess and replace parts randomly. Using high-quality gasoline and regularly cleaning throttle body carbon buildup helps prolong component life. Address abnormal sounds immediately, or minor issues may escalate into major repairs that hurt your wallet.

[LaOlive]

I think the sudden unpleasant noise from the USR125 is very dangerous, as it may mask other warning sounds or signals. An unstable engine operation can lead to reduced power output, causing sluggish responses during braking or turning. A loose belt or chain increases friction noise significantly, and high-speed riding may easily result in chain breakage and accidents. Exhaust leaks might also release toxic gases, affecting health. When I encountered a similar issue, I pulled over to inspect, checking the tension of the fan belt and looking for cracks on the muffler's exterior. Safety comes first—don't cut corners; sending it for professional repair is the safest option. After all, abnormal noises are often warning signs, and timely action ensures safety for yourself and your companions on the road.