Known as the MSX125 outside North America, the Honda Grom is a 124.9cc air-cooled single-cylinder mini motorcycle produced since 2014 in the US market (2013 globally). Manufactured in Thailand, the Grom has sold over 750,000 units worldwide and supports an enormous aftermarket parts and customization scene. Despite its small displacement, the Grom has gone through four distinct styling and mechanical updates, each affecting parts compatibility. Sun Coast carries used Grom components from our Odessa, Florida facility, each piece photographed and cataloged individually.
Grom generation and parts compatibility
| Generation | Years (US) | Key changes |
|---|
| Gen 1 | 2014-2015 | Launch model. 124.9cc SOHC single, 4-speed transmission, high-mount exhaust, round headlight, 10hp. |
| Gen 2 | 2017-2020 | Stacked LED headlight, low-mount exhaust (moved from high to under-seat), restyled bodywork and fuel tank, ABS option added (2018+). Engine and frame unchanged. |
| Gen 3 | 2022-2024 | New 5-speed transmission (up from 4), redesigned bodywork with quick-release panels, new LCD dash with gear indicator, revised engine for Euro5 compliance. Frame geometry unchanged. |
| Gen 4 | 2025+ | Restyled bodywork (sportier tank shape, new side panels), same 5-speed engine and frame as Gen 3. Primarily cosmetic update. |
The 124.9cc engine is fundamentally the same across all years, but the 2022+ models have a fifth gear and revised internals for emissions compliance. Engine bottom-end components (crankshaft, cases) interchange across all generations, but the 5-speed transmission gears and shift drum from 2022+ do not fit the earlier 4-speed models. Bodywork is the major compatibility divider: each generation has unique plastics, and the Gen 1 high-mount exhaust system and Gen 2+ low-mount systems are completely different. Frame and swingarm are consistent from Gen 1 through Gen 4, so suspension components, wheels (12-inch front and rear), and brakes interchange across all years. The 2018+ ABS model adds a front wheel speed sensor and ABS modulator not present on non-ABS bikes. The Honda Monkey 125 shares the same engine family but uses a different frame, swingarm, and wheels, so only engine internals cross between the two.
Common Grom failure points and replacement parts
The Grom has no NHTSA recalls and no systemic mechanical failures. It is one of Honda's most reliable platforms. Virtually all replacement parts purchases are either crash damage or cosmetic customization rather than mechanical failure.
Crash and tip-over damage: Due to its small size, low weight, and use as a beginner/stunt/urban bike, the Grom suffers more cosmetic damage than most motorcycles. Levers, mirrors, bar ends, bodywork panels, and foot pegs are the most commonly replaced items.
Exhaust corrosion (Gen 2+ low-mount): The under-engine exhaust routing on 2017+ models is more exposed to road spray and debris than the Gen 1 high-mount design, and the stock exhaust header can develop surface corrosion over time. This is cosmetic unless it progresses to a perforation.
Chain and sprocket wear: The small-diameter sprockets on the Grom wear faster than on larger motorcycles. Frequent adjustment and replacement at shorter mileage intervals is normal.
Commonly replaced Grom parts
- Bodywork panels (crash damage and customization)
- Levers and mirrors
- Exhaust (aftermarket upgrades are extremely popular)
- Chain and sprockets
- Brake pads
- Handlebars and grips
- Foot pegs and rearsets
Frequently asked questions
Q: Will 2014-2015 Grom bodywork fit a 2017-2020 model?
No. The Gen 1 (2014-2015) and Gen 2 (2017-2020) have completely different body panel shapes, headlight designs, and exhaust routing. The Gen 1 uses a high-mount exhaust and round headlight; Gen 2 uses a low-mount exhaust and stacked LED headlight. Frame and suspension components do interchange, but all bodywork is generation-specific.
Q: Can I put a 5-speed transmission from a 2022+ Grom into an older 4-speed model?
This is not a straightforward swap. The 5-speed transmission uses a different gear set, shift drum, and shift forks that require splitting the cases. While the cases are physically similar, the internal arrangement differs enough that this is considered a complete engine swap rather than a simple parts transplant. Most owners seeking more gears on a pre-2022 Grom opt for an aftermarket close-ratio kit designed for the 4-speed cases.
Q: Do Honda Monkey 125 parts fit the Grom?
The Monkey 125 shares the same engine family as the Grom, so internal engine components (piston, valves, crankshaft, oil pump) interchange. However, the Monkey uses a different frame, different wheel sizes (12-inch vs the Grom's 12-inch, but different hubs and spokes on some markets), different bodywork, and different exhaust. Chassis and body components do not cross between the two.
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