The current bike uses the RS 125 name again, on the four-stroke that started as the RS4. The brief is honest about the calendar. One source says the rename was 2016, another 2017, another 2019. This page uses “about 2017” and does not pretend the three dates have been reconciled. To verify against the manufacturer’s own model year before you write a dating letter or buy a fairing from the wrong restyle.

Power, and the licence

The 2025 update is the clean figure: 15 hp (11 kW) at 10,500 rpm. The brief states the kilowatts in the same breath as the horsepower, and 11 kW is the A1 ceiling on GOV.UK, alongside 125 cc and 0.1 kW/kg, from age 17. The 2021 Euro 5 figure is 15.2 hp at 10,750 rpm. The brief does not convert that 15.2 hp into kilowatts and does not say whether it sits inside the cap. To verify. Do not “round it down” and tell a learner it is legal, and do not tell an owner it is illegal, on the back of a unit conversion this site has not sourced.

There is still no full-power two-stroke hiding in this bike. Derestriction guides written for a RAVE valve and a Nippondenso CDI do not apply.

What changed in the metal

The brief’s body notes are short: restyles, and a wider rear tyre. The tyre size is To verify. A wider rear tyre is not a licence to fit a two-stroke wheel, and the wheel bearing is a separate unknown. Euro 5 is the 2021 update. Euro 5+ is the 2025 update. What those did to the silencer, the mapping or the intake is not in the brief.

Factory codes are To verify. The year-letter table in the brief stops at C for 2012. Later letters exist in ISO 3779 — the decoder will show them and mark them — and they have not been checked against a current RS 125 plate. S is both 1995 in the brief and 2025 in the ISO cycle. On a new four-stroke that clash matters. Read the plate with the model, not the letter alone.

Faults and the GP Replica

Common problems are To verify. The brief had no owner-forum list. Valve clearances, oil grade, coolant, plug and torque are in the same state. The GP Replica of 2017–18 is the livery named for this generation. It is listed in the generation record rather than in the older verification table.

The D50B0 warning from the RS4 page still stands. That is a 50 cc engine. Nothing in the two-stroke parts categories fits this motorcycle.