46 Sandstone Ave, Naracoorte
South Australia, 5271
The all-new 125cc 2-stroke engine is the most powerful unit ever used on the YZ125, and it develops a higher performance in the mid to high rpm range and offers improved usability. This has been achieved by developing an all new cylinder head, piston and cylinder, con rod, crank, YPVS as well as redesigning other major components.
The bodywork is the slimmest ever, with the area between the rider’s knees 36mm narrower than on the previous model, and the athletic and modern body design underlines the YZ125’s lightness and compactness. The reduced dimensions improve overall rider mobility and reinforce the feeling of agility.
Following extensive testing Yamaha’s engineers have developed a new intake system. The whole area around the airbox has been redesigned including the seat base, rear frame and sidepanels in order to reduce air resistance, making a significant contribution towards increased intake efficiency.
The YZ125 is equipped with a Keihin PWK 38.1mm carburettor featuring a solenoid controlled Powerjet that instantly delivers its fuel/air mix for even more explosive performance, giving a real advantage out of the gate and when accelerating hard out of corners. And the new TPS (Throttle Position Sensor) and 3D map controlled CDI ensure optimised ignition timing, while the new VForce reed valve assembly provides optimum intake efficiency at all engine speeds.
The transmission has been redesigned and features a new set of internals to handle the YZ125’s dramatically increased maximum power output, and a redesigned shift mechanism gives a smoother shift feeling. The secondary reduction ratio is slightly increased with the use of a 13/49 front/rear sprocket set, and for better driveability the transmission runs with slightly reduced 5th and 6th gear ratios.
Yamaha’s SSS (Speed Sensitive System) KYB front forks are widely regarded as being amongst the best designs available on a production motocross bike, and the new model features revised low speed damping settings on both the front and rear suspension systems for better handling characteristics.
Complimenting the performant aluminium semi-double cradle frame, the new rear frame on the YZ125 is designed to enhance air flow into the carburettor, and a new style cross member facilitates the use of a new single bolt fixing for the seat – for quicker and easier maintenance. The new rear frame also accommodates a new mounting point for the 50mm shorter silencer.
The brakes on the YZ125 have been redeveloped to handle the increased performance. The front disc diameter remains the same at 270mm, but a new more rigid twin-pot caliper is equipped with larger 25.4mm pistons and new pads with an increased contact area for more powerful braking. For the rear disc, the diameter is reduced by 5mm to 240mm while the pad area remains the same.
Engine performance is just one element of being competitive – the ability to handle the power effectively and take total control of the chassis is also vital. A new much flatter seat with a lower front and higher rear, together with the new slimmer tank and narrower radiator shrouds, make it much easier to shift your weight around the bike when braking, accelerating and cornering.
