If you've spent any time staring at your bike in the garage, you've probably realized that swapping the honda msx swingarm is one of the quickest ways to transform the whole look of the machine. Let's be honest, the stock swingarm that comes on the MSX125—or the Grom, depending on where you live—isn't exactly a masterpiece. It's a functional, heavy, black steel box section that does the job, but it doesn't exactly scream "custom build."
Upgrading this single component can change your bike's personality in two ways: how it feels through the corners and, perhaps more importantly for many of us, how it looks when it's parked at the local meet. Whether you're going for a sleek racing vibe or that long, low-drag look, the swingarm is the backbone of that transformation.
Why Even Bother Replacing the Stock Arm?
You might be wondering if it's worth the hassle. I mean, the original one holds the wheel on just fine, right? Well, sure. But the stock honda msx swingarm is made of heavy steel. In the world of small-displacement bikes, weight is the enemy. Every ounce you can shave off the "unsprung weight"—that's the stuff not supported by the suspension, like your wheels and swingarm—makes the bike feel more flickable and responsive.
When you switch to a high-quality aluminum swingarm, the difference is immediate. The rear end of the bike feels less "thumpy" over potholes, and the suspension can actually do its job because it's not fighting the momentum of a heavy metal beam. Plus, let's face it: the stock chain adjusters are a pain. Most aftermarket options come with much nicer integrated adjusters that make tightening your chain a five-minute job instead of a frustrating ordeal.
Finding the Right Style for Your Build
Not all swingarms are created equal, and the one you choose depends entirely on what you want your MSX to be. There are generally three paths you can take here.
The Standard Length Aluminum Upgrade
If you love the way the MSX handles—short, snappy, and wheelie-prone—you probably want to stick with the standard length. An aluminum replacement in the stock dimensions keeps that "toy-like" agility but adds a massive amount of "bling." These are usually CNC-machined and look like pieces of jewelry. They're often braced, too, which adds some rigidity if you're pushing the bike hard on a track or through some tight canyon roads.
The "Stretched" Drag Look
Then there's the stretch. If you've seen those Groms that look like they belong on a drag strip, they're running an extended honda msx swingarm. Usually, people go for a +4 inch or even a +6 inch extension.
Stretching the bike does a few things. It makes the bike much more stable at high speeds (if you've tuned your engine to actually go fast), and it makes it much harder to accidentally loop the bike during a hard launch. Most people do it for the aesthetics, though. A stretched MSX has a presence that's hard to ignore, giving it a "big bike" silhouette that confuses people who don't know what they're looking at.
The Braced "Racing" Style
Braced swingarms have an extra loop of tubing—usually on top—that reinforces the structure. Does a 10-horsepower bike really need a braced swingarm for structural integrity? Probably not. Does it look absolutely sick? Absolutely. It gives the rear end a beefy, industrial look that mimics high-end liter bikes.
What to Look for When Buying
When you start shopping for a honda msx swingarm, you'll see prices ranging from "suspiciously cheap" to "I could buy another bike for that." It's tempting to go for the cheapest option on a random auction site, but you really get what you pay for here.
Material Quality You want 6061 or 7075-T6 aluminum. This isn't just about weight; it's about the thing not snapping when you hit a speed bump. Cheap alloys can be brittle. A good swingarm should have clean, consistent welds or, if it's a modular design, high-quality bolts.
Pivot Bearings vs. Bushings This is a big one. The pivot is where the swingarm attaches to the frame. The stock one uses rubber bushings, which are okay but can feel a bit mushy. Higher-end aftermarket arms use needle roller bearings. These allow the swingarm to move up and down with almost zero friction, which makes your rear shock feel way smoother. If you're spending the money, try to find one that includes quality bearings.
Chain Adjusters Check out the mechanism for adjusting the chain. The best ones use a captive system where the axle stays aligned as you turn a bolt. It's way more precise than the old "plate and nut" system on the stock bike.
The Reality of Handling Changes
It's important to talk about how a new honda msx swingarm changes the ride. If you stay with the stock length, the change is mostly positive—better suspension response and a lighter feel.
However, if you go for a stretch, you're changing the geometry of the bike. A longer wheelbase means a larger turning radius. That "flickability" the MSX is famous for? You're going to lose some of that. It'll feel more planted and less twitchy, which some people actually prefer, but it won't dive into corners quite as fast. Just something to keep in mind before you commit to that +10cm extension.
A Few Things You'll Need for the Install
Swapping the swingarm isn't the hardest job in the world, but it's not a five-minute task either. If you're doing this yourself, there are a few extra bits you'll probably need to pick up.
- A Longer Chain: If you're going with an extended honda msx swingarm, your stock chain won't reach. You'll need a new 420-pitch chain (or 428 if you've done a conversion) with more links.
- Longer Brake Lines: Again, if you stretch the rear, that rear brake caliper is moving further away. You'll need a longer braided stainless steel line to reach it safely.
- A Proper Stand: You can't use a standard swingarm paddock stand while you're actually removing the swingarm. You'll need to support the bike by the frame or the engine to get the rear end off the ground.
- Grease: Don't skimp on the waterproof grease for the pivot bolt. You want that thing to stay quiet and move freely for years.
Maintenance and Upkeep
Once you've got your shiny new honda msx swingarm installed, you can't just forget about it. Aluminum is great because it doesn't rust like steel, but it can still oxidize or get pitted if you live near the ocean or ride on salted roads in the winter.
If you got a polished finish, you'll want to hit it with some aluminum polish every few months to keep that mirror shine. If it's anodized (colored), be careful with harsh wheel cleaners, as some chemicals can actually fade the color over time. Just some mild soap, water, and a bit of wax is usually enough to keep it looking fresh.
Also, since you've likely replaced the pivot point, it's a good idea to check the torque on that main pivot bolt after your first 100 miles. Everything "seats" in a little bit, and you don't want any play in the rear end of your bike.
Final Thoughts
At the end of the day, upgrading your honda msx swingarm is one of those mods that offers a massive "bang for your buck" in terms of visual impact. It completely cleans up the rear of the bike and gives it a premium, custom feel that the stock parts just can't match.
Whether you're building a show bike or a daily commuter that you just want to look a little cooler, it's a solid investment. Just make sure you think about how you want the bike to handle before you decide on the length. Once you see that CNC-machined aluminum glowing in the sun, you'll realize it was worth every penny. Happy wrenching!