
Adding a rear trunk to a motorcycle without applying for modification registration is considered illegal modification. Here is a partial introduction to vehicle modifications: Relevant regulations include changing the body color; replacing the engine; replacing the body or frame; replacing the entire vehicle due to quality issues; changing the use nature from commercial to non-commercial or vice versa; the vehicle owner must apply for modification registration at the local vehicle management office. Legal basis: According to the law, no unit or individual may assemble a motor vehicle or alter the registered structure, construction, or characteristics of a motor vehicle without authorization.

I believe adding a top case is definitely a modification, but it falls under the category of mild and practical customization. When motorcycles leave the factory, their rear structure is fixed. Installing a top case requires specialized mounting brackets and fixtures, which essentially alters the vehicle's frame. I've seen people even modify the position of the rear seat handrails to accommodate larger top cases. Although this type of modification isn't a major overhaul, it does change the bike's appearance and weight distribution. However, most vehicle management offices are quite lenient with such modifications—as long as the top case doesn't obstruct the license plate and the brackets are securely installed, it generally passes annual inspections. It's advisable to check the vehicle registration photo; if the bike originally came with a top case, it needs to be documented. Also, pay attention to weight balance during daily rides—I once had a close call while carrying a full load of fishing gear on mountain roads.

Technically speaking, installing a top case is considered a modification. The motorcycle registration certificate includes vehicle photos and dimensional parameters, and adding a top case alters the body length and weight. I've helped friends install top cases from several different brands and found that the original screw holes don't always align, often requiring adapter brackets or drilling modifications. This is much more complex than simply mounting a phone holder. However, the practicality is undeniable—it provides storage for helmets and rain gear. During traffic stops, police mainly check if the license plate or brake lights are obstructed. I've seen cases where oversized top cases resulted in fines. I recommend choosing a model with a quick-release function, which can be removed in seconds during annual inspections. Be cautious during installation to avoid damaging the turn signal wiring—I once crushed the wiring during a modification.

Installing a top case is definitely considered modification. Motorcycles are designed with front and rear weight distribution in mind. Suddenly adding a metal box at the rear completely changes the center of gravity. After installing a top case on my naked bike, the leaning sensation felt strange during cornering. The key point is the installation process: the original rear grab rail needs to be removed, holes drilled for the mounting bracket, and over a dozen screws tightened - if this isn't modification, then what is? Some large top cases even require reinforced baseplate support, which means modifying the frame. The benefit is doubled storage space - you won't even need to carry a backpack for grocery runs. However, I've been stopped by traffic police twice, fortunately without fines as the case size was compliant. Remember to choose a model with ventilation holes to prevent your helmet from getting stuffy and smelly in summer.


