Just How Fast is the RS125?

The RS125 delivers unrivalled performance in the 125cc class. Check out these specs.

Engine

• Single cylinder
• 2-Stroke
• Liquid cooled
• Aluminium cylinder with Gilnisil coating on barrel
• Reed intake and exhaust port control valve
• Separate lubrication
• 54 mm bore
• 54.5 mm stroke
• 124.8cc displacement
• 12.5 ± 0.5:1 compression ratio
• Dell’Orto PHBH 28 BD carb
• CDI capacitor discharge electronic ignition
• Electric start
• 12V – 180 W generator
• Separate mixing lubrication system with variable displacement volumetric pump
• Six speed gearbox
• Chain driven
• Multiple disk wet clutch
• Cast aluminium sloping twin-spar frame with thin walled structural shell and cross rib reinforcement
• Upside-down hydraulic action front telescopic fork (40 mm diameter inners) and wheel travel 120 mm)
• Cast aluminium swing-arm rear suspension with asymmetrical members, thin walled structural shell, single hydraulic monoshock, adjustable spring preload, wheel travel 120 mm
• 320 mm front disk brake with floating caliper and four parallel pistons
• 220 mm rear disk brake and twin piston caliper.
• Aluminium alloy wheels 3.00 x 17″ front and 4.00 x 17 ” rear
• Tubeless radial tyres
• Front tyre 110/70 ZR 17″
• Rear tyre 150/60 ZR 17″
• Maximum length 1,950 mm
• Maximum width at handlebars 720 mm
• Maximum height at windshield 1,135 mm
• Seat height 805 mm
• Wheelbase 1,345 mm
• Tank capacity 14 litres (3.5 litre reserve)
• Price £3,724 OTR

The Aprilia RS 125 is a GP derived replica that looks the part but offers performance that is practically unrivaled in the 125cc class. In full-power trim, the bike develops 33bhp which is the maximum you will be able to ride on a restricted license. This translates to 0-60 in about 6 seconds and a top speed of around 100mph.

All that power from a 125cc engine means that it won’t run forever and it will need occasional rebuilds. However, if you respect the bike, allowing it to warm up properly and avoiding wide-open throttle for too long then the engine will offer surprising longevity.

Click here to read about buying a second hand Aprilia RS 125.

The bike offers two power outputs; a restricted 14bhp and a derestricted 33bhp. If you’ve just done your CBT then you can ride the 14bhp format with L-plates. Once you’ve got your fill license you can pay somewhere between £50-£400 (depending on what’s already on your bike and who does the work) to derestrict the bike and more than double its power output.

Click here to read about derestricting the Aprilia RS 125

.

How to fit steel braided brake lines to your Aprilia RS125

Thanks toAndyS_RS on TJ Tuning who inspired this post.

Fitting braided brake hoses will not give you greater stopping power, but it will give improved feel which is crucial to effective braking. This guide describes how to bleed the front brake. The process is the same for the rear brake, but bleeding is easier and can generally be done without removing the calliper.

Install the steel braided hose and bleed your brakes

• Empty the line by bleeding the brake.
• Connect hose to the nipple and loosen
• Pump the brake and it should eject fluid, which you can collect in your container.
• Keep the brake attached to the bike while you do this.
• Once the reservoir is empty, stick a clean rag in, soak up remains and prevent intake of dust.
• Loosen the master cylinder banjo bolt (beneath the banjo bolt there is a small ball bearing, be careful not to lose it).
• Use a rag to mop up any drips.
• Take the loose end of the hose, place it into your container and then place the container as low as possible.
• Fluid should drain into the container.
• Disconnect the hose from the caliper once it has stopped.
• Remove the calliper from the fork but there will still be fluid in it so keep it upright.
• With the hole into which brake fluid flows carefully positioned over your jam jar, squeeze the pads apart and it will eject most of the remaining fluid into the container.
• Remove the pads from the calliper and clean it thouroughly.
• Check that your new hose is of equal length to the rubber hose it will replace.
• Ensure it is properly routed.
• Take the new bolts from the box and reinstall the calliper
• Connect both ends of the hose and tighten up the new banjo bolts.
• Ensure that the small ball bearings have been replaced and that copper washers have been installed on either side of the new hose.
• Fill the reservoir half full with your new brake fluid and start bleeding the brake(this will take a while as the system needs to be primed with new fluid).
• Top up the reservoir as required.
• When you reach a point that you feel is acceptable take the bike out a few times and the leaver will get firmer with each use.
• On your return, flush a few more measures of fluid through the line and top up the reservoir (the instant you open the bleed valve it will go spongy, but close it up and it will get firm very quickly).