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First ride: Aprilia RS4 125

For the first time on a sports 125, Aprilia now have a bike that features a four-stroke engine

Since 1993, more than 100,000 RS 125 two stroke bikes have been manufactured around the world. Aprilia are still making this legendary learner legal for the foreseeable future, but with 2-strokes sadly dying a slow death they need a four stroke solution. Their answer? The brand new RS4 125.

The RS4 125 will certainly be cheaper to run and not require the love and care that the RS 2 stroke does. Sure, it’s not going to be as fast as the RS is, but it can still deliver big smiles.

Aprilia obviously has a wealth of experience when it comes to building winning bikes and the RS4 125’s chassis is a lightweight ‘state of the art’ affair with die cast aluminium spars with cross reinforced ribs.

The RS4 is powered by a new water cooled 4-stroke 4-valve DOHC engine that features a Magneti Marelli electronic injection system. Output is 15bhp, the maximum allowed for leaner legal bikes.

With Aprilia belonging to the same group as Derbi, there are some similarities with the Derbi GPR 125 bike. The Aprilia’s engine does feature a larger piston though that gives the engine a deeper sound whilst the riding position is also lower.

Just as Yamaha’s YZFR-125 came along 3 years ago and gave 125 sports bikes a fresh style, Aprilia have now moved that on and for my money, the RS4 is the clear winner in the looks department.

The new bike is certainly a stunner and it is no surprise that it owes those looks to its big SBK winning big sister, the 1000cc RSV4 APRC.

The bike’s fairings were designed in a wind tunnel to offer both wind protection whilst maintaining aerodynamic efficiency. They appear exactly like the ones found on the litre bike. The exhaust integrated into the lower fairing is also a very nice touch.

The colour schemes ‘racing white’ and ‘racing black’ colour schemes are also a copy of the larger bike and by creating an identical look, Aprilia have given this 125 a big look and feel.

Just as the wind tunnel will have helped the bike go as quickly as possible, when it does come time to slow down, the RS4 125 also does this in style too. The bike features a 300mm disc up front which is easily stopped with the radial four piston caliper.

When you also consider this 125 has a pair of black anodized 41mm upside down forks as well, you can appreciate the high spec this bike has. It’s serious, but also serious fun.

The bike was launched at the 1.7-mile handling circuit at the Vairano testing ground, just outside of Milan. Apparently Ferrari uses the circuit but I had 15 horses to play with instead of a prancing one.

Power delivery is smooth if uneventful, and limited at 11,000 rpm. The only time you will see the needle hit 13,000 is when you turn the ignition on and the analogue and digital dash lights up with an appropriate ‘125’.

It’s pretty much a linear delivery without much excitement but as with all small bikes, the fun is had in conserving the speed you have slowly built up.

The standard bikes shown were fitted with Slovenian ‘Bogart’ tyres and have a 130 section on the rear. The press bikes however were wearing super sticky Supercorse SE1 tyres (150 rear section) meaning you could get away with murder in the corners.

The bike handled great and once up to speed and tearing around corners the smiles kept coming. The track took a few laps to learn but the bike allowed you to easily change lines mid corner and all the UK journos were upset when our fourth and final slipstreaming session finally came to an end.

When comparing this bike to other sports 125s, a real ace up its sleeves, albeit one priced at an additional £100, is the optional quickshifter. This is the first time a quickshifter has been available on a mass produced 125 and a massive weapon in bragging rights.

Some shifts seemed a bit clunky but the quickshifter worked best when the bike was just hitting the limiter, allowing you to keep the throttle open while you upshift, eventually hitting sixth gear whilst tucking in as much as possible.

The brakes worked well and everything felt really nice although the suspension was a little on the soft side. The bikes were constantly on the go during the day and if petrol and time allowed, would probably still be haring round the track now.

As a teenager I sadly never had £3999 to spend on a bike and had to make do with rusty C90s and dodgy TZRs. For those that have an industrial sized piggy bank or at least parents who can splash that amount of cash, this bike will be surely be top of the sports four stroke wish list.

Aprilia also had a new bike on show at the launch. To confuse matters it is still part of the new RS4 family but this one is a 50cc, 6 speed 2 stroke called the RS4 50.

Although not available to ride, it shares the same looks as the rest of the family. The only clues giving it away from the 125 where the protruding exhaust and a gold chain.

Aprilia were obviously keen to mention their strong racing heritage at the RS4 launch, especially in the smaller capacity leagues. Biaggi may have won the 2010 WSB championship on a 1000cc RSV4 (of which there is a tasty looking RS4 125 rep available) but the Roman Emperor is well known for his success onboard the Aprilia RS 250cc bikes.

Rossi, Melandri, Stoner, Simoncelli and current Moto GP champion Lorenzo have all cut their teeth on low capacity Aprilia racing bikes and in its relatively short history, the Italian manufacturer has notched up 45 world titles, 36 of them in Moto GP.

I don’t know if the new 50 and 125cc bikes will be responsible for any more future racing greats but there is no denying that they certainly look the part and both models tick a lot of boxes. And if they get more people into biking then that can only be a good thing.

I do know that with the naked KTM Duke grabbing the recent ‘125’ headlines, it would be great to have a drag race between that and the RS4 125. I’ll take the Aprilia, but to be on the safe side I’d better have the quickshifter too.