New 125cc motorcycles | 2021 Aprilia RX 125 and SX 125 enduro & supermotard

Updated for 2021, Aprilia has reinvented the SX (supermoto) and RX (enduro) 125cc motorcycles for white-knuckling down back roads and trails in style.

Aprilia RX SX 125 2021

APRILIA has just released details on the new RX and SX 125cc motorcycles, the latest editions to their range for riders (young or old) looking for a sporty, demanding and thrilling ride. 

Focus and time has been spent optimising the riding performance for riders, with changes to the engine unit and base functions, which are shared between the two. Then, as is tradition, the RX is fitted for the trail-riders with more off-road touches, whilst the SX is optimised for road use. Could these could be the best 125cc motorcycles released in 2021?

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Both RX and SX motorcycles share the same liquid-cooled, 4-stroke, single-cylinder 125cc motor, with DOHC and 12:1 compression ratio. The motor will provide top of the category performance, legal for CBT and A1 riders with power outputs of 11kW / 14.75bhp @ 10,000rpm, and 11.2Nm of torque at 8,000rpm. The torque curve and maximum power is now developed at lower revs, and paired with a 6-speed transmission, which makes all the difference on lower capacity machines. 

The engine unit has seen a raft of updates, including a new intake and air filter, new iridium spark plug, new head for the redesigned combustion chamber, redesigned exhaust line and end can, and new Marelli MIUG4 ECU amongst other tweaks. On the road, this will translate into much more responsive performance.

Both RX and SX boast advanced suspension, 41mm USD front fork with 240mm travel, and at the rear a swingarm with monoshock and 210mm travel. Both are also fitted with new digital instruments, easy to read as well, they say!

The Aprilia SX 125 is fitted with spoked wheels - 17 inch front and rear - with 300mm front disc and 220mm rear. The RX 125 has spoked wheels, but they’re larger knobblies, 21-inch front and 18 inch rear, with wavy discs: 260mm front and 220mm rear. Both make use of Bosch ABS with anti-roll-over mode - a first for 125cc machines. 

Both weigh in at a light 134kg wet (7-litre fuel tank), which for a 125cc machine with peak possible power means maximum thrills on and off-road. Seat heights are 880mm for the SX, and 905mm for the RX. 

The Aprilia RX 125 and SX 125 are both available in Silver Speedway and new Rally Tribute graphic variant colourways, with a Red Raceway variant also available for the SX 125.

Both of these look like superb fun to ride, on or off road, and could well be at the top of my list to ride in 2021... I knew a couple of green lanes that are calling the RX name...

Check out the Aprilia site for more info.

Aprilia SX 125 and RX 125 - Technical Data Sheet

Engine type

Single-cylinder, 4-stroke, 4-valve, DOHC, liquid cooling

Bore and stroke

58 x 47 mm

Total engine capacity

124.2 cc

Compression ratio

12.0~12.6 : 1

Max Power

11 kW at 10,000 rpm

Maximum torque at crankshaft

11.2 Nm at 8,000 rpm


ECU Electronics Magneti Marelli MIUG4 ø 32 mm




Wet sump


6 speed, drive ratio:

1st 11/33

2nd 15/30

3rd 18/27

4th 20/24

5th 25/27

6th 23/22


Multi plate wet clutch

Primary drive

Straight cut gears, drive ratio: 29/69

Final drive

Chain, drive ratio:

SX: 13/62

RX: 13/69


Twin-tube steel frame

Front suspension

Upside down fork with Ø 41 mm stanchions, 240 mm excursion

Rear suspension

Steel swingarm, monoshock with progressive link system, wheel travel 210 mm



Front: Ø 300 mm stainless steel disc with floating calliper

Rear: Ø 220 mm stainless steel disc with floating calliper


Front: Ø 260 mm disc with floating calliper

Rear: Ø 220 mm disc with floating calliper

Metal-braided connecting hoses.


SX: Front: 2.5 X 17" rear: 3.5 X 17”

RX : Front: 1.85 X 21" rear: 2.15 X 18”


SX: Front: 100/80 – 17” rear 130/70 -17”

RX : Front: 90/90 – 21” rear 120/80 -18”


Max. length: 2075 mm (RX 2145 mm)

Max. width: 820 mm

Wheelbase: 1425 mm (1430 mm)

Max. height: 1140 mm (RX 1180 mm)

Saddle height: 880 mm (RX 905 mm)


134 Kg (kerb weight with full fuel tank)

Consumption (WMTC cycle)

2.6 l/100 km

CO2 Emissions (WMTC cycle)

60 g/km

Fuel tank capacity

7 litres