December 1, 2011

Yamaha's lightweight retro 125cc motorcycle

The Yamaha Y125 concept

Yamaha's press conference at the Tokyo Motor Show today was a genuine sign of the times. Four brand new world premiers were shown. The largest internal combustion engine amongst them was a 250cc model with fat tires designed to go anywhere - the SUV of motorcycles was the claim.

The Yamaha PASThe Yamaha EC-Mui The Yamaha Y125 concept

There was also a three-wheeled electric commuter, a fold-up electric pedal-assist bicycle and, wait for it, an 80 km/l (226 mpg Imperial or 188 U.S. miles/gallon) retro 125cc commuter that's somewhere between a bicycle and motorcycle - it weighs just 80 kg and it is beautiful.

Firstly, the I've always been a big fan of 125cc four-strokes - it happened about 30 plus years ago when I was testing a 125cc Kawasaki for a motorcycle magazine and at the end of a week of valve-bouncing and lane-splitting, found I'd managed close to 100mpg for the daily commute. It was around the time of the first energy crisis and I figured that I'd found the answer.

If a high-revving, OHC four-stroke could achieve close to a 100 mpg when being shamelessly mistreated, what sort of economy could it deliver if it were tuned for economy, ridden gently and placed in a suitably lightweight frame?
Yamaha's Y125 appears to answer that question. Modeled on Yamaha's first motorcycle, the YA-1, the Yamaha Y125 is a modern interpretation of that motorcycle. Though the YA-1 was itself a copy of the German DKW RT125 and was powered by a two-stroke engine, I am certain readers will agree the Yamaha concept has faithfully updated the YA-1.

The YA-1 weighed around 140 kilograms and produced 5.6 bhp @ 5000 rpm for what was at the time, a highly competitive motorcycle not just on the road, but on the racetrack.
The big difference with the Y125 is in the fuel consumption. Yamaha claims the bike uses its "world" 125cc four-stroke motor, though the engine certainly seems to have been lightened and polished and beautified, and heaven knows what they've done with the internals.

The Y125 uses what is by today's standards, close to a bicycle frame with sophisticated lightweight suspension and similarly, the brakes are also featherweight. The end result is a bike that tips the scales at 80 kg - just a tad more than half the original YA-1's total.

At this stage, it's a concept but who knows what might happen simply because it's such an enticing bike that takes everything back to basics. Sure, the lights are LED and the rear wheel is driven by a belt rather than a chain, but nothing seems like rocket science - it's just a very traditional basic design updated with modern day computer design and material science, and it is an absolute celebration of the form of the original Yamaha.

The "world" motor Yamaha claims is used in the bike produces double the horsepower of the original YA-1, so the Y125 will never be embarrassed for acceleration or top speed on urban roads. The 80kg weight will ensure it is far quicker than your average scooter to ride, and the fuel consumption of 80 km/l (226 mpg Imperial or 188 U.S. miles/gallon) is testimony to what can be done when you really want to achieve economy in a two-wheeler.

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