In stock form, the Honda Grom typically tops out around 55–60 mph (88–97 km/h) on level ground with a light rider; real-world speeds vary by weight, wind, and road conditions. This article focuses on the standard Honda Grom MSX125 street model.
This piece explains the bike’s speed characteristics, what factors push or limit its top speed, and what riders commonly experience across typical setups and model years.
Stock performance and key specs
Below are the core numbers you’ll see in dealer brochures and owner manuals for the current Grom family.
Core specifications
- Engine: 124.9cc air‑cooled single-cylinder, 6‑speed transmission.
- Estimated peak power: roughly 9–10 hp depending on year and tuning.
- Top speed (stock): about 55–60 mph (88–97 km/h) on flat ground with a typical rider.
- Curb weight: around 229 pounds (about 104 kg).
- Seat height: ~30 inches (around 760 mm).
The Grom is designed to be light and nimble rather than a highway-sprinter, so the top speed figures reflect urban and suburban riding expectations as much as straight‑line performance.
What affects top speed
Several factors determine the actual top speed you’ll see, beyond the manufacturer’s published number.
- Rider weight and posture, which influence wind resistance and acceleration.
- Riding conditions, including altitude and air density.
- Gearing and final-drive setup, which trade acceleration for higher top speed.
- Engine health, maintenance, and component condition (air filter, spark plug, throttle response).
- Intake and exhaust modifications, and ECU remapping or fuel management.
- Tire size and tire pressure, which affect rolling resistance and grip.
In practice, a lighter rider in good conditions will typically reach the familiar stock ceiling more consistently, while heavier riders or headwinds can shave a few mph off the top regardless of setup.
Common setups and expected speeds
Riders typically pursue a few common paths to speed, from keeping the bike stock to adding modest modifications or larger engines. Here’s what you can expect in typical scenarios.
- Stock, unmodified Grom: roughly 55–60 mph (88–97 km/h) on level ground with a normal rider.
- Moderate intake/exhaust upgrades and ECU tune: often 60–65 mph, depending on the tune and fuel quality.
- Gearing tweaks or larger bore kits (150–190cc) with performance exhaust and proper remap: often 65–75 mph; some setups can reach mid-70s under ideal conditions.
These ranges reflect common DIY and aftermarket configurations. Real‑world results vary with part quality, the tuning approach, and rider weight.
Summary
The Honda Grom is tuned for agile urban riding rather than long highway sprints. In stock form expect about 55–60 mph on flat terrain; with careful mild modifications you can push into the low to mid-60s, and larger engines or significant gearing changes can push toward the mid-70s under favorable conditions. Always ride within the bike’s design limits and follow local laws.