2018–2024 · Supermoto · Buyer's Guide
125cc With Real Corners
Aprilia built the SX 125 around a liquid-cooled 124 cc single making 15 hp at 10,000 rpm and 9 lb-ft, the same motor that powers the RS 125, hung in a supermoto chassis with an upside-down fork, 17-inch wheels and a 6-speed box. The bodywork is the real trick. It is sharp, angular and unmistakably Aprilia, so from twenty feet away it reads like a full-size machine rather than a small-displacement one. The rest is deliberately simple: ABS is the electronic safety net, and everything else is done by geometry, wide bars and 300 lb of bike.
On the road it behaves like a bicycle with an engine. Long suspension travel front and rear turns broken city pavement into a non-event, and 67 mpg matters because the tank only holds 1.9 gal. This is a machine for city miles and tight second-gear back roads, and it is genuinely good at both. The honest caveat is the ceiling. Top speed is 60 mph, so any route with a freeway in it becomes a chore, and the 34.6 in seat rules out a lot of riders before they get that far. Buy it for the roads you can reach without a highway.
Spec sheets don't ride bikes, but they set the baseline.
| Power | 15 hp (11 kW) @ 10,000 rpm |
|---|---|
| Torque | 9 lb-ft (12 Nm) |
| Displacement | 124 cc |
| Engine | Single-cylinder |
| Cooling | Liquid-cooled |
| Gearbox | 6-speed |
| Fork | Upside-down (USD) |
| Front tire | 100/80-17 |
| Rear tire | 130/70-17 |
| Ground clearance | 6.5 in (165 mm) |
| Front travel | 9.4 in (240 mm) |
| Rear travel | 8.7 in (220 mm) |
| Seat height | 34.6 in (880 mm) |
| Wet weight | 300 lb (136 kg) |
| Fuel capacity | 1.9 gal (7.2 L) |
| Top speed | 60 mph (96 km/h) |
| Fuel economy | 67 mpg (US) |
Equipment check
Safety
This part isn't my riding impression. It's what I've picked up from riders over the years: paddock talk, chats with owners at bike nights, and the steady stream of messages that land in my inbox from people living with the bike. On the SX 125 the picture is consistent. Owners talk about how it rides and how cheap it is to run far more than they talk about anything else, and the complaints they do raise are small and mostly cosmetic.
The one thing riders come back to is how planted the SX feels. The soft suspension and 17-inch sports tires give it a substance most 125s never manage, and owners say it corners with real confidence instead of the nervousness they expected. Running costs get almost as much praise. The liquid-cooled single sips fuel at around 67 mpg and has held up over serious mileage on basic maintenance. Riders also like that the ABS works on the front wheel only, so braking stays in their hands without the system stepping in uninvited, and plenty of them mention the aggressive styling and inverted fork as looking well above the price.
The gripes are quieter. A few owners find the exhaust note flat and short on character for an Italian badge, and swap the silencer. Others mention the dash leaving out a fuel gauge, which means watching the trip meter and waiting on the reserve light. A handful report the finish on fasteners and minor parts going off after a few years, particularly on bikes ridden through wet winters.
Random engine cut‑out at high rpm when warming up
At least two owners reported the engine momentarily cutting out at high rpm shortly after a cold start; the bike runs fine once fully warm, but the issue is unnerving and may point to a fueling or sensor glitch.
ABS sensor/wiring connectivity issues
A loose connector at the Bosch ABS control unit can cause the ABS warning light to stay off or the speedometer to read zero, reducing brake safety. Reseating the connector fixes the fault.
Water pump failure at moderate mileage
One report of water pump failure after approximately 6,000 miles (9,600 km), resulting in coolant loss and potential overheating if not caught early.
Premature ignition coil failure
A few owners experienced ignition coil pack failure very early in the bike’s life (within the first two months of ownership), leading to misfires or no‑start conditions.
Where this Aprilia SX 125 pulls ahead of — or falls behind — its rivals on the numbers, and the typical bike in its class on character.
Power
Torque
Displacement
Wet weight
Seat height
Forget spec-sheet bragging. Here's who the SX 125 is actually built for.
Your commute and your Skyline coffee runs are exactly where this bike shines, and it has the presence to look right parked next to anything. Plan routes that keep you off the freeway, because 60 mph is the whole story.
Made for Bay Area Ridge Roads · San Francisco / Bay Area · Skyline Boulevard / Alice's Restaurant
It will teach you more about corner speed than most things with real power, but you will be wide open everywhere and slow on the straights. A blast on tight canyon roads, out of its depth on the fast ones.
Made for Angeles Crest Highway · Coronado Trail / US 191 · Highway 1 / Big Sur
For repeat runs on tight, technical corners this is a real skill tool, since you carry momentum instead of horsepower. The problem is the approach ride: any highway miles to get there will wear you down.
Made for Back of the Dragon · Blue Ridge Parkway · Cherohala Skyway
If this one isn't quite the fit, these are the bikes worth riding back-to-back against it.
Any price note compares both bikes at the same age — the youngest age both have on the used market — against this Aprilia SX 125. “cheaper/pricier” is what that bike costs second-hand, not how worn it is.
