Technical philosophy remained
The YZF-R125 finally continues Yamaha’s line of 125cc supersport bikes after a few years of absence in this category. The original bike’s philosophy has pretty much remained unchanged: a full size supersport machine with a competitive 125 cc engine. Its predecessor, the legendary 2-stroke TZR 125 was actually based on the highly competitive TZR 250. It shared the same frame and other components with the 250cc version. The YZF-R125 follows the same lines in development. However, years ago one could simply take a 250cc model and put a 125cc engine into the chassis; nowadays Yamaha needed to apply different methods. There is no 250 that could be used as a suitable donor machine and the R6 is simply too big to use for a 125cc machine.

Design principle from R6
Project leader Toshiharu Shigeta explains: ”We developed this 125cc with a similar philosophy to the R6. Riding fun on winding roads was high on our priority list. The chassis geometry of the YZF-R 125 has similarity with the R6. At the same time we also achieved a very good handling in city traffic, because of sporty geometry in combination with low weight.”

The YZF-R125 size is bigger than most 125 machines, because chassis and components take influence from bigger bikes and make this 125 cc machine feel and perform like a real super sports machine. “The rear swing arm is a fully new design, because we needed a part with more stiffness to achieve the riding character we were looking for.” knows Shigeta.

Project chief Sabino Tisci talks about an interesting details solution: “A must for every real sports bike is centralised mass for good handling. We used the R6 muffler layout, with its chamber under the engine and a short muffler sticking out on the right side behind the foot pegs. We could have chosen to use an ‘up-muffler’ under the seat, which may look cool, but makes the bike more top heavy. Also this allowed us to save space under the seat for the electric components. This design principle makes this 125cc’s handling character so great.”

R series styling
“Yamaha really wanted to make the YZF-R125 part of the R-series. Therefore we asked Kazumasa Sasanami, who gave the R1 its characteristic looks, to draw the lines” confirms Oliver Grill, Product Planning Manager at Yamaha Motor Europe. You can clearly see the design elements that link this machine to its bigger brother(s).

New engine
To support the sporty looks and chassis, Yamaha developed a completely new engine. The single cylinder four-stroke engine uses the latest technology and complies with future emission regulations. It has a 4 valve cylinder head and is liquid cooled. The EU 125cc licence sets a power limit at 15 HP. “We tried to make the best within this regulation” confirms Toshiharu Shigeta. The result is a lively ‘regulation conforming’ engine with a good character and torque. “We even developed a new six speed gearbox to suit European traffic speed and road conditions. The well-balanced gearbox supports the riding fun you have with this little supersport machine on small country lanes, without compromising the city riding or the highway speeds."

Sketches during the development of the new YZF-R125 2008