Parts directory
- Categories by generation. Prices are empty on purpose.
- OEM numbers stay empty until they are copied from a catalogue.
- Do not buy 123 parts for a 122, or Rotax parts for a four-stroke.
Directory
Slots, not prices.
OEM numbers and prices are empty on purpose. Enter an OEM number only when it has been copied from the official parts catalogue for that VIN, and enter a price only with the date it was seen. Do not fill either from memory or from a forum.
No parts match those filters. Clear them to see the full directory.
Top end
Rotax 122 and Rotax 123 top ends do not share pistons, barrels or gaskets. Identify the engine before ordering.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Piston 122 and 123 pistons do not interchange. Order against the engine casting, not the registration year. Sizes are not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, Pedparts UK, Wemoto, Aprilia UK dealers |
| Piston rings MCN's maintenance guide, via the brief, says rings around every 5,500 miles. The ring end gap is not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, Pedparts UK, Wemoto |
| Cylinder / barrel Cylinders do not swap between the 122 and the 123. MCN's interval for piston and barrel is around every 10,000 miles. Bore sizes are not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, Pedparts UK, eBay UK |
| Reed block and petals Inspect petals for chips. The allowable closed gap is not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, Pedparts UK, Wemoto |
| Cylinder head O-ring Replace rather than reuse. Section and part number are not recorded here. 122 and 123 are not the same part. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Aprilia UK dealers, eBay UK |
| Base gasket Gaskets do not swap between the 122 and the 123. Thickness is not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, PJ Motorcycle Engineers, Aprilia UK dealers |
Bottom end and clutch
Crank, main bearings, seals, gearbox and clutch. The 123 clutch is fastened with a nut. The 122 clutch is not.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Crankshaft The brief says Pedparts lists a Rotax 122 crankshaft. A 123 crank is not the same part, and many 123 parts are discontinued. No OEM number is copied here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Pedparts UK, PJ Motorcycle Engineers, eBay UK |
| Main bearings Crank bearings are a known bee-tail complaint. Bearing numbers are not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, eBay UK, Aprilia UK dealers |
| Crank seals A leaking crank seal leans the engine out. Sizes are not recorded here. Do not guess a seal from the other Rotax. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, PJ Motorcycle Engineers, eBay UK |
| Clutch The brief records a nut on the 123 clutch and no nut on the 122. Baskets, plates and the fastening do not swap. Torque is not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Aprilia UK dealers, eBay UK |
RAVE powervalve
Blade, blanking plate, solenoid, cable and the control unit. Restricted bikes may have a blanking plate instead of the blade.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| RAVE blade The derestriction steps in the brief say the blade goes taper down, flat side up. Confirm that orientation in the manual for your year. To verify the part number. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, eBay UK, Aprilia UK dealers |
| Powervalve blanking plate Fitted in place of the RAVE blade on many restricted bikes. The brief does not list a part number. The Extrema/GS had no factory-restricted version, per Hartrusion. | Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK |
| RAVE solenoid The brief includes a 12 V solenoid test. A seized solenoid is a known bee-tail fault. Connector pinout is not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK, Aprilia UK dealers, Wemoto |
| RAVE cable Adjustment method and free play are not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, eBay UK |
Carburettor
Three Dell'Orto carburettors across the two-strokes. Jet sizes are not a catalogue entry until they are copied from the manual.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Dell'Orto VHSB 34 The 34 mm carburettor on the Rotax 123. PJME is named in the brief as a supplier of 34 mm carburettors. | Extrema / GS, Round-light RS 125 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, eBay UK |
| Dell'Orto PHBH 28 The 28 mm carburettor on the Rotax 122, until the Euro 3 VHST. Not every round-light bike has one: UK and much of Europe kept the 123 and the 34 mm carb into about 1997–98. | Round-light RS 125, Bee-tail, RSV-style | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, eBay UK, Pedparts UK |
| Dell'Orto VHST 28 Euro 3 carburettor, with a throttle-position sensor and a carburettor heater. | Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, eBay UK, Wemoto |
| Jets, needle and slide No baseline jetting chart is printed on this site. One derestriction blog, via the brief, mentions a main jet moving up from 115 on a 28 mm carb. That is one account, not a factory baseline. To verify. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, Pedparts UK, eBay UK |
Ignition and electrics
SEM on the 123, Nippondenso CDI on the 122, and an EFI Technology ECU from the Euro 3 bikes.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| SEM stator 123 ignition. The brief says SEM stators are hard to find. Not used on the 122. | Extrema / GS, Round-light RS 125 | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK |
| Nippondenso CDI 122 ignition. The brief describes an environmental retard around 5–6,000 rpm. How the bridge differs by unit is To verify. Do not follow a pinout that is not in the manual for that CDI. | Round-light RS 125, Bee-tail, RSV-style | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK, Aprilia UK dealers |
| EFI Technology ECU Combined ECU on the Euro 3 bikes (about 2008 onward in the brief). Pinout not recorded here. | Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, eBay UK |
| Throttle-position sensor and carburettor heater Fitted with the VHST 28. The brief also lists air-temperature and extra-air sensors on this generation. Individual part numbers are not recorded. | Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, Wemoto |
| Immobiliser / alarm Owners report trouble with the factory immobiliser on the RSV-style bikes. No repair procedure is copied here. | RSV-style | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers |
| Mechanical tacho drive shaft The brief says this shaft is fragile and no longer available. | Extrema / GS | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK |
| Rear-wheel speed sensor The RSV-style digital dash takes road speed from a rear-wheel sensor rather than a gearbox drive. | RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, eBay UK |
Cooling and oil
Water pump, thermostat, oil pump and feed lines. Warm the engine to 60°C before hard riding (MCN, via the brief).
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Water pump Seal and impeller part numbers are not recorded here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Aprilia UK dealers, eBay UK |
| Thermostat Opening temperature is not recorded here. The 60°C warm-up figure is a riding practice from MCN, not a thermostat rating. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Aprilia UK dealers |
| Coolant Type and mix are not recorded here. To verify in the manual before buying a premix. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop |
| Oil pump and feed lines The two-strokes use a pumped oil feed. Stroke, ratio and the grade of oil are not recorded here. MCN says to use a premium two-stroke oil. Do not ride with an empty oil tank. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, eBay UK, Wemoto |
Exhaust
Expansion chamber, and a catalyst in the chamber from 2003. Corrosion is a repeated owner complaint.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Expansion chamber From 2003 the SF, and the later two-strokes, have a catalyst in the chamber. The Euro 3 bike has two catalysts. A non-catalyst pipe is part of the derestriction path in the brief. Brand names and part numbers are not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | PJ Motorcycle Engineers, eBay UK |
| Secondary air system Added on the SF for 2004, and present on the later two-strokes as the SLS / extra-air hardware. Individual parts are To verify in the catalogue. | Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, Aprilia parts catalogues |
Brakes
Axial front calipers to 2005. Radial front calipers and braided lines from 2006. Fluid grade is not recorded.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Front brake pads, axial caliper Through the bee-tail (to 2005). Compound and part number are not recorded. | Extrema / GS, Round-light RS 125, Bee-tail | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Sportsbikeshop, eBay UK |
| Front brake pads, radial caliper RSV-style onward for the two-stroke. Four-stroke calipers are not described in the brief. To verify before ordering pads for an RS4 or a current RS 125. | RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Sportsbikeshop, Aprilia UK dealers |
| Brake hoses Braided lines are standard on the RSV-style bike. Hose type on earlier generations is To verify. Banjo torque is not recorded. | RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop, Wemoto |
| Brake fluid DOT grade is not in the brief. To verify in the manual or on the reservoir cap before opening the system. Do not mix grades. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop |
Suspension and bearings
USD fork seals, shock, headstock bearings and wheel bearings. Oil weight and sag are not recorded.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| USD fork seals and oil The RSV-style bike has a new fork. Seal size, oil weight and air gap are not recorded, including for the four-strokes. To verify. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Sportsbikeshop |
| Rear shock Linkage lengths and spring rates are not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK, Aprilia UK dealers |
| Headstock bearings Bearing numbers are not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, eBay UK |
| Wheel bearings Sizes are not recorded. The later four-stroke has a wider rear tyre; the size is To verify, and the bearing may not match a two-stroke wheel. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Sportsbikeshop |
| Speedo drive The brief says speedo drives wear out on the bee-tail. The RSV-style dash uses a rear-wheel sensor instead. | Extrema / GS, Round-light RS 125, Bee-tail | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK, Wemoto |
Bodywork and decals
Fairing shape, headlight and decal kits differ by generation. A replica kit does not change the mechanical bike.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Replica decal set Decalmoto is the kit supplier named in the brief, at roughly €95–€140. That is not a GBP price. Match the kit to the year and the bodywork, not just the colour name. A 1998 Chesterfield scheme is not in the sourced livery list. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Decalmoto |
| Headlight unit Rectangular on the Extrema/GS, round with a lip on the 1995/96–1998 bike, then the bee-tail shape, then twin headlights on the RSV-style and Euro 3 bikes. Four-stroke lamps are not catalogued here. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | eBay UK, Aprilia UK dealers |
| Fairing brackets and fasteners Brackets differ by generation. Do not force a bracket from another bodywork onto this frame. Sizes are not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3, RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers, eBay UK, Aprilia parts catalogues |
Four-stroke service
RS4 125 and the current RS 125. The engine is the Derbi GPR125-derived 124.2 cc unit, not the RS50's D50B0.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| Spark plug Heat range and reach are not in the brief. The BR8EG and BR10EG named elsewhere are from a two-stroke derestriction guide. Do not assume they fit this engine. To verify. | RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop, Aprilia UK dealers |
| Air filter Part number not recorded. Do not order an RS50 filter. | RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Wemoto, Aprilia UK dealers |
| Injector and fuel-system service Both four-strokes are fuel injected. Pressures, part numbers and the fault list are To verify. No owner-forum fault list was in the brief. | RS4 125, RS 125 four-stroke | Not recorded To verify | Not recorded No date, because no price has been entered. | Aprilia UK dealers |
Two-stroke spark plugs
The derestriction steps name an NGK BR8EG and a colder BR10EG. That is one guide's advice, not a page from the workshop manual.
| Part | Fits | OEM number | Last price | Suppliers |
|---|---|---|---|---|
| NGK BR8EG Named in the brief's derestriction steps as the plug you are coming from. Confirm it is the manual's plug for your engine before fitting. To verify against the workshop manual. Gap is not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop |
| NGK BR10EG Named in the same steps as the colder plug after derestriction. One blog's advice. To verify against the workshop manual. Gap is not recorded. | Extrema / GS, Round-light RS 125, Bee-tail, RSV-style, Euro 3 | Not recorded To verify | Not recorded No date, because no price has been entered. | Sportsbikeshop |
Suppliers named in the brief
These are ordinary links to the sites the brief named. Tracked affiliate links are a separate slot and stay invisible until an ID is set in the environment. See the README.
| Supplier | Useful for | Affiliate scheme |
|---|---|---|
| Pedparts UK (opens in a new tab) | Dedicated RS/RX/MX 125 section; the brief says the range lists a Rotax 122 crankshaft. | To check |
| Wemoto (opens in a new tab) | UK online pattern and OEM-style parts, with an Aprilia range. | None found |
| PJ Motorcycle Engineers (opens in a new tab) | UK RS125 specialist: pistons, barrels, big-bore kits, 34 mm carburettors. Recommended by MCN. | To check |
| Aprilia UK dealers (opens in a new tab) | Genuine parts through authorised dealers. | No |
| Aprilia parts catalogues (opens in a new tab) | Exploded diagrams and OEM part numbers. The linked PDF is the RS 125 2006–2010 catalogue only. | No (reference) |
| Decalmoto (opens in a new tab) | Replica decal kits. The brief records a rough price of €95–€140, which is not a GBP price. | To check |
| Sportsbikeshop (opens in a new tab) | Consumables, tools and riding kit. | Yes: 8% new customers / 2% returning, 10-day tracking. Programme not connected on this site. |
| eBay UK (opens in a new tab) | Used and NOS parts, and breakers. | Yes (eBay Partner Network). The 2019 UK rate card in the brief says 2.5% for vehicle parts. Rate to verify. Programme not connected on this site. |
Rates the brief wrote down
None of these programmes is connected. The rates are here so they are not forgotten, and so the doubtful ones stay marked.
- eBay Partner Network: vehicle parts and accessories at 2.5% on the 2019 UK rate card. To verify the current rate.
- Amazon Associates UK: automotive 5%, other categories 3%, as recorded in the brief.
- Sportsbikeshop: 8% for new customers, 2% for returning customers, 10-day tracking.
- Demon Tweeks via Awin: motorcycle about 3%, 30-day cookie, from a third-party summary. To verify.
The 2006–2010 parts catalogue PDF is the reference for OEM numbers in that span. Numbers are not copied into the tables above until a person has checked the diagram for a specific VIN.
Sources
- Aprilia RS125 parts and engine ID (opens in a new tab) — PJME
- RS50 D50B engine (opens in a new tab) — Pedparts
- RS 125 2006–2010 parts catalogue (PDF) (opens in a new tab) — Aprilia Superstore
- RS 125 replica decal sets by year (opens in a new tab) — Decalmoto
- Affiliate programme (opens in a new tab) — Sportsbikeshop
- Associates commission rates (opens in a new tab) — Amazon UK
- EPN UK rate card (2019) (opens in a new tab) — eBay
- RS 125 (1995–2012) review and buying guide (opens in a new tab) — MCN
Research brief dated 24 October 2026. Where this page says “the brief”, that is the sourced master plan behind the first edition.