We would like to thank Massimo Russo for contributing to this article.
The RX bikes from 1984 to 1988 are still part of the older enduro generation from Noale and were joined by the MX125 unplated and unapproved and the Tuareg Rally for marathon use. All three bikes were also available in a 250 version. The 125s were powered by the Rotax 127, which was also used on the Aprilia ETX and Tuareg (non-Rally model), but they had a cast-iron jacketed cylinder and mixer and no balancing countershaft to dampen vibrations. The forks were of the traditional type with dust covers. The "old" versions of the RX 125 had drum brakes replaced by a mixed disc-drum system from 1985, were not fitted with a mixer and the plastics were not painted.
1990: RX 125 - Type FD
The new generation of RX 125 (Six Days) arrived in 1990, offered in a single blue and lilac colour scheme. The first series was characterised by the type code FD and had homologated code DGM 52824 OM. The shapes were new and well cared for, angular but not too much, the plastics were painted and of excellent workmanship. The RX '90 will be the only model to have a "flat" front mudguard and will also feature red painted wheel hubs. In addition, the rear light and number plate will be mounted on a removable matt black plastic support that is also supported by a black metal frame, which is also removable.
The frame was based on that seen on the '89 Tuareg Rally, but the headstock angle and trail were changed to offer greater stability, with the main single girder part with a split cradle at exhaust level and a detachable rear seatpost frame that housed the passenger footpegs, oil pan, filter box and battery. The fork was upside-down 40 mm in diameter and 300 mm of travel and the rear monoblock was a refined Sachs-Boge adjustable in compression and rebound with 30 different positions, with 290 mm of travel, which for the first time was mounted on a 125 Aprilia. The stand, a feature inherited from the old Tuareg Rally of 84/87, is central and becomes a distinctive feature of the new enduro of Noale.
The engine is the classic Rotax 123 2-stroke with a six-speed countershaft. The cylinder is identified by the number 223610 and is the first cylinder to have boosters on the exhaust port introduced on an Aprilia, later also intended for stradali AF1 Futura Sport Production and Extrema SP (with some variation on the ports), characterised by a very sharp delivery. The carburettor is a Dell'Orto VHSB 34 LD, while the exhaust valve is the electronically controlled RAVE 2 already introduced in 1989 on stradali Sintesi and Pegaso. The crankcases are brown powder coated.
1991: RX '91 - GP Type
The 1991 Six Days, type code GP with homologation code DGM 53067 OM, replaces the 1990 Six Days and is presented in elegant dark purple and metallic silver colours with more rounded shapes than the previous version and a new front mudguard. With this bike Stefano Passeri won the 1991 World Team Championship in the Six Days of France.
The changes introduced are:
- The frame remains the same, but the rear seatpost frame is different, more tapered on the left side due to the smaller 4Ah battery.
- The swingarm is an all-new rectangular-section light alloy, with forged and welded ends on the main drawn arms, while rear wheel removal is made quicker and more practical by the adoption of a wheel axle with a suitably shaped head.
- Suspension sees a new 40mm Marzocchi fork with 300mm of travel, while at the rear appears a new version of the Boge-Sachs APS adjustable shock with 300mm of travel.
- The brakes see a new 250mm front disc (260mm the previous one) served by a twin-piston caliper. At the rear, the disc is 220mm in diameter with a fixed caliper. Both discs feature slots. New front brake caliper.
- The aluminium hubs are also new, losing the characteristic red colour of the first version and having 32 spokes instead of the previous 36, with a weight saving of 200 grams at the front and 600 at the rear.
- The engine is the same as the previous Rotax 123 with some improvements, including the cylinder with serial number 223616 with exhaust booster, which, while maintaining the power of 223610, has a softer delivery and therefore more suitable for the intended use of the bike. The carburetion is revised (the VHSB 34 LD carburettor remains) as well as the filter box and muffler. The gearbox is renewed with the first three gears closer together, while the final drive is slightly shortened from 14/148 to 14/49. The crankcases are now painted grey as on all Rotax '91.
1992: RX '92 - Type GF
1992 is the year of the yellow, red and purple 125R World Championship Replica and the dark blue, aquamarine green and white Control Data. The livery of the 125R WCR is a tribute to the livery of the Portuguese rider Miguel Farrajota who took part in the 1991 championships with the Model M Six Days painted in this way, while the Control Data was the livery used by Stefano Passeri in the 1992 world championship.With the new chassis the stability of the bike increases considerably, the solidity of the front end is marked but the rider's position is more collected, the footrests are higher and set back making the bike slightly more uncomfortable and tiring on long stretches.
- The changes introduced are as follows:
- The structures are completely redesigned with the two side conveyors taking on a more rounded shape and wrapping around the radiator more tightly, while the curvature of the long seat is less pronounced than before. The lines of the side number plates and rear wing have also been simplified. Now the bike is even more refined, the plastics are better connected, the shapes are round and the plastic number plate holder, which has disappeared the number plate holder frame, is redesigned and more modern.
The fuel tank went from the meagre 9 litres of the '90 and '91 models to 12 litres of this '92 model and also lost the two side appendages that descended downwards and made access and maintenance of the spark plug, carburettor and thermic unit difficult. The loss of these volumes and the further increase of three litres will result in a fuel tank shape that is less bulky in height but much wider and, although pleasing to the eye and appropriate, will certainly make the bike a little less manoeuvrable when standing because of the greater width between the knees.
- The frame is completely new and has undergone a radical overhaul to make it more suitable for off-road use. Note the reinforcement at the swingarm pivot point, with the swingarm now 15mm longer than before, and the position of the shock absorber has been changed to lower the centre of gravity.
- The fork only sees the adoption of a different internal setting.
- The wheel hubs are new and allow the fitting of 36 spokes instead of 32 as in the previous version.
- The braking system uses a new front floating caliper with the front disc gaining 10mm in diameter, returning to 260mm. In addition, both discs lose their lowered socket head screws and gain more common countersunk Allen screws and the rear disc, due to structural fragility, remains slotted but loses half the slots compared to the previous one.
- The engine is still the excellent Rotax 123, of the third generation, with revised internal parts, the clutch housing (as can be seen from the different external shape compared to the previous version) and an extra coupling at the front. The crankcases were simplified internally, the desmodromic gearbox was revised to have a softer gear change, the fourth and fifth gears were reversed, a new mixer and the position of the rev counter gears (not present on the RX) were moved to the front.
1993: RX 125 '93 - Type HT
The two 1992 bikes were virtually identical in 1993, the 125C in yellow, plum purple and magenta and the new Control Data, almost identical in graphics but dark blue, lilac and white. The 1993 Control Data was the first RX to have a body-coloured frame rather than a white one. The only substantial technical difference compared to the 1992 N model is the 19 inch rear wheel instead of 18, therefore with a more motocross vocation, the result of testing and trial work on the race tracks. The bike is homologated with both sizes, however, given the current difficulty in finding 19-inch enduro tyres homologated for road use.
1994: RX 125'94 - Type
In the 1994 model the frame remains the same (it becomes matt grey) but the plastics change and become even more cross-country. The whole look of the bike changes substantially, from the fluorescent red and matt grey colour, to the headlight holder, the side number holders, the radiator shrouds and the seat. The only component that will remain the same for the future will be the front mudguard. From here on, the frame, plastics and technical characteristics will remain more or less the same. Two colour variants are available: red-grey with black number plates or blue-grey with red number plates.
Among the technical innovations introduced are:
- Completely revised swingarm made of light alloy with variable rectangular cross-section offering greater resistance to torsion and stress in general.
- The suspension department sees a new fork with 40mm stanchions and 275mm of travel, adjustable in both compression and rebound damping with two knobs at the ends of the stanchions.
- The engine remains the same as the '93 version, but the crankcase is cast in a new aluminium-silicon alloy that ensures greater resistance to breaking and yielding loads, a modification extended to all '94 Rotax 123s. The primary gear is lightened with 24mm diameter holes.
1995: RX 125 '95 - Type MT
In 1995 the RX was radically updated with a redesigned chassis and, as with all Aprilia 125 production, received the new Rotax 122 engine. The proposed colour scheme is a single black/grey.
In detail, the changes adopted are:
- Although the frame appears to be the same as the '94 version, it has been completely redesigned, so much so that its compact dimensions allow the seat to be lowered by 3cm and more ground clearance to be obtained, thanks also to new side reinforcement plates at the swingarm. This also increases the rigidity of the structure.
- The fork remains the fully adjustable 40mm unit introduced with the '94 version, but is upgraded in calibration along with the rear suspension for smoother ride.
- The front brake benefits from a larger master cylinder.
- The new Rotax 122 definitively retires the previous 123. It is a lighter engine, more precise in machining and coupling and easier to maintain, which compared to its predecessor adopts the following changes:
- The thermic unit adopts the code 223618 (indicated on the right side as before), also known as 220H, (written on the intake in the area close to where the reed valve is mounted) which is a specific cylinder for the Rotax 122 and not interchangeable with those specifically for the Rotax 123. The differences are minimal. The new cylinder is only flanged differently on the crankcase and the cylinder head studs have 8 holes instead of 7 holes (for reliability, the studs often tore in the prepared 123s). From 1997 a new cylinder head was adopted which contained less water to increase the flow rate.
- The exhaust system with expansion now has a carbon finish.
- The VHSB 34 LD carburettor is retained and fitted with a new filter box.
- The ignition system is completely revolutionised in the Rotax 122: the simple and economical SEM ignition of the Rotax 123 is replaced by a Kokusan with a dedicated control unit and variable advance.
- The clutch is removable and now, while maintaining the same discs as the Rotax 123, it is possible to work on the component without the use of pneumatic guns as was the case with the Rotax 123. The gear selector is removable: another gem not present in the Rotax 123.
1996: RX 125 '96 - type MT
The RX 125 '96 is only updated with a new, unique orange/grey colour scheme. All engine and chassis components remain unchanged from the '95 model.
1997: Aprilia RX 125 '97 - Type
The first RX 125 depowered to 15 hp. Two new colours are introduced: orange/grey similar to the '96 version, but with different graphics and a new blue/grey.
The RX 125 was finally superseded in 1999 by the Aprilia MX 125, which shared its chassis and mechanics, but with revised bodywork aesthetics and 17-inch stradali motard wheels.