2011–2016 · Supersport · Buyer's Guide
Real Grip, Learner Displacement
The RS4 125 is a proper Aprilia shrunk down to 125 cc. It has an aluminum perimeter frame, sharp Italian bodywork and a liquid-cooled single that makes 15 hp at 10,500 rpm and 8 lb-ft at 8,500 rpm. On paper that is modest. What sets this generation apart is the packaging: a 130/70-17 rear tire, a six-speed gearbox and a chassis that looks and feels far more serious than this class usually gets. Among small sport bikes, this is the one that feels like you bought the real thing and not a starter kit.
It rides light and eager, and it rewards a rider who keeps the single spinning and carries speed instead of waiting for drive. Aging is where you need to be honest with yourself. Chain wear, a weak stock tensioner, higher oil use and electrical trouble around the stator and dash mean a used one needs a careful inspection and a regular check routine. There are no rider aids at all: no ABS, no traction control, and no suspension adjustment front or rear. For a newer rider building real technique, it's a great tool. An experienced rider will run out of engine long before the chassis runs out of ability.
Spec sheets don't ride bikes, but they set the baseline.
| Power | 15 hp (11 kW) @ 10,500 rpm |
|---|---|
| Torque | 8 lb-ft (11 Nm) @ 8,500 rpm |
| Displacement | 125 cc |
| Engine | Single-cylinder |
| Cooling | Liquid-cooled |
| Gearbox | 6-speed |
| Final drive | Chain |
| Front tire | 100/80-17 |
| Rear tire | 130/70-17 |
| Seat height | 31.9 in (810 mm) |
| Wet weight | 265 lb (120 kg) |
| Fuel capacity | 3.8 gal (14.5 L) |
Equipment check
Drivetrain
I've been collecting what owners say about this bike for years: paddock talk, chats at the gas pump, club-night stories and the messages riders send me directly. For the RS4 125 the picture is fairly clear. Owners rank it among the best small sport bikes of its day, and their complaints are few and specific.
Riders consistently put the RS4 125 at the top of its class. They point to the mix of build quality, sharp handling and styling that set it apart from rivals. Many say it's genuinely involving to ride despite modest power, and they credit the agile chassis and a responsive engine for that. Some owners single out the solid materials. A few note that the four-stroke needs maintenance less often than high-strung two-stroke rivals.
The gripes come up less often. Riders coming off older two-stroke 125s find it noticeably heavier and say that takes some edge off its agility. Some mention the footpegs touching down fairly early when they push hard in corners. Heavier riders report the engine feeling strained, with acceleration turning leisurely. Price comes up too, since it cost more than many rivals, though owners who raise it tend to accept the components and handling as the reason.
Stator wires fraying on flywheel
Stator wires can rub against the flywheel, causing potential electrical failure.
Fuel pump reliability issues
Fuel pump failures have been reported, though the fix is considered straightforward for DIY mechanics.
Premature chain wear and tensioner problems
The stock chain tensioner is reported as inadequate, leading to rapid chain wear and frequent adjustments.
Electrical gremlins and dashboard malfunctions
Owners report intermittent electrical issues, including erratic dashboard behavior and general electrical unreliability.
Higher than expected oil consumption
Some owners note the engine consumes more oil than typical, requiring regular checks and top-ups.
Where this Aprilia RS4 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 RS4 125 is actually built for.
Skill over speed is exactly what this bike is about. It's light, eager in tight turns and teaches you to carry momentum. Just check the chain before every run to the mountains.
Made for Back of the Dragon · Blue Ridge Parkway · Cherohala Skyway
If you already run the canyons on a big bike, 15 hp won't hold your interest for long. As a light second bike for sharpening your lines on the tight sections, it can still earn its spot.
Made for Angeles Crest Highway · Coronado Trail / US 191 · Highway 1 / Big Sur
For a Saturday loop out of Austin it's fun and cheap to run, but the long straights between the twisty bits will show up its 15 hp. Keep the rides local and it makes sense.
Made for Austin / Texas Hill Country · Twisted Sisters · Austin / Handbuilt Motorcycle Show
If this one isn't quite the fit, these are the bikes worth riding back-to-back against it.
Successor · 2016–2022
125cc Chassis With Real Bite
Successor · 2017–2018
RSV4 Looks, Learner Laws
Competitor · 2011–2016
Lightweight City Learner Done Right
Competitor · 2008–2014
Full-Size Soul, Learner Limits
Competitor · 2025
Serious Corner Tool, Tiny Engine
Similar Character · 2004–2010
City Light, Built Right