2008 Aprilia SX 125 & RX 125 First Look

November 6, 2007
JC Hilderbrand
JC Hilderbrand
Off-Road Editor|Articles|Articles RSS|Blog |Blog Posts |Blog RSS

Hilde is holding down the fort at MotoUSA's Southern Oregon HQ. With world-class dirt bike and ATV trails just minutes away, the hardest part is getting him to focus on the keyboard. Two wheels or four, it doesn't matter to our Off-Road Editor so long as it goes like hell in the dirt.

The new Aprilia RX 125 is targeted at young riders looking for a way into the lightweight  street-legal  performance 2-stroke category.
The new Aprilia RX 125 is targeted at young riders looking for a way into the lightweight, street-legal, performance 2-stroke category.

Aprilia has introduced a pair of new machines at the Milan Show that support the radical V-Twin SXV and RXV off-road lineup. The advanced 450 and 550 machines are a big handful for any youthful rider to straddle, but the market for attracting young riders is an important one in the dirt world. Now, with the introduction of the RX 125 and SX 125, youth can start their riding careers on the Italian brand.

The new sibling machines share virtually everything with one another in terms of motor, chassis, suspension and bodywork. The primary differences are in the wheels and tires where the motard-style SX uses 110/70-17 and 150/60-17 front and rear. The enduro RX model is equipped with a 90/90-21 front and 120/90-18 rear. Final gearing on the SX is a 16/45 combo while the RX uses a 49-tooth rear sprocket. Internal ratios for the six-speed transmission are identical.

The 125cc 2-stroke motor is nearly square with a 54 x 54.5mm bore/stroke and a 12.5:1 compression ratio to deal with at the kickstart lever. Fuel is fed to the water-cooled engine through a 28mm Dell’Orto carb while burnt fumes are expelled at the Euro 3 emission standards via an elongated expansion chamber and stinger. Premix is distributed remotely so riders won’t have to bust out their Ratio Rite while filling the 2.6-gallon tank.

Aprilia mounted the one-two-five engine inside a double-cradle steel frame. The chassis uses a double-trellis beam on each side, somewhat similar to the upper portion of the RXV/SXV frames. The swingarm is listed as steel on the spec sheet as well. A 40mm inverted fork and linkaged rear shock suspend the entire package. Part of the unsprung weight is a set of fairly large binders. The floating twin-pot front unit squeezes a 260mm rotor while the 220mm rear disc is controlled by a single-piston caliper.

If we can’t even get the biggest OEMs to import their 125cc motocrossers, don’t hold your breath for this baby to arrive on American shores. The market for street-legal 2-strokes is virtually nonexistent.

The styling is standard Aprilia off-road fare - and by that we mean sharp and sexy.
The styling is standard Aprilia off-road fare – and by that we mean sharp and sexy.

Aprilia SX 125 Technical Specs (RX differences in parentheses)
Engine: Liquid cooled, single cylinder 2-stroke. Aluminum cylinder with Nikasil coated liner. Read valve intake. Separate mixing. Homologated to Euro 3 standard.
Fuel: Lead free petrol.
Bore by stroke: 54 x 54.5mm.
Displacement: 124.8cc.
Compression ratio: 12.5:1.
Carburetor: Dell’Orto VHST 28.
Ignition: Electronic CDI ignition.
Starting: Kick start
Alternator: 12 V – 180 W
Lubrication: Separate mixing with variable displacement, volumetric pump.
Gearbox: 6 speed. 1st 10/30 2nd 14/29 3rd 17/27 4th 19/25 5th 21/23 6th 22/21
Clutch: Multi-plate wet clutch.
Primary drive: Helical gears, 19/63.
Final drive: Chain: 16/45 (16/49)
Frame: High strength steel frame with double trellis beam and double cradle. Separate seat frame.
Front suspension: Upside down telescopic fork, 40 mm. Wheel travel 10.2 inches.

For those riders with fewer dirt aspirations  the SX 125 is a motard version but virtually identical except for the wheels and tires.
For those riders with fewer dirt aspirations, the SX 125 is a motard version but virtually identical except for the wheels and tires.

Rear suspension: Steel swingarm. Hydraulic monoshock with piggy back cylinder. Wheel travel 10.6 inches.
Brakes: Front: 260 mm disc, floating caliper with two parallel pistons. Rear: 220 mm disc, floating caliper with single piston.
Wheels: Aluminum. Front: 3.00″ x 17″. Rear: 4.25″ x 17″. (Front: 1.60″ x 21″. Rear: 2.15″ x 18″)
Tires: Front: 110/70 x 17″ Rear: 150/60 x 17″. (Front: 90/90 x 21″ Rear: 120/90 x 18″)
Overall length: 85.2 inches
Overall width at handlebars: 33.1 inches
Overall height: 46.1 inches
Seat height: 34.3 inches
Wheelbase: 58.3 inches
Fuel tank: 2.6 gallon (0.3 gallon reserve)