End of the two-stroke?

November’s season-ending Valencia Grand Prix will be a historic event for motorcycle racing – the last two-stroke GP. The racing two-stroke has been legislated out of existence, largely at the whim of the Japanese bike industry.

First of all, the wicked old 500s were replaced by friendlier four-stroke MotoGP bikes, then last year the sublime 250s were axed in favour of Moto2 and finally the little 125s will be replaced by Moto3 four-strokes from 2012. Valencia will thus be an emotional moment for fans (me included) who will miss the spine-tingling crack of two-stroke engines being warmed up in pitlane.

Two-strokes ruled bike racing for several decades, following ex-Nazi rocket scientist Walter Kaaden’s groundbreaking work on the engine in the 1950s and ’60s. Domination began with the smaller classes – 50, 125 and 250cc – but by the mid-70s the technology had seen off the mighty MV Agustas in the premier 500 class. Until the rules were rewritten in 2002 to allow 990cc four-strokes to compete with the 500s, a four-stroke hadn’t won a 500 GP since Giacomo Agostini and his MV ruled at a damp Nürburgring in August ’76. A few years later Honda spent a fortune on its oval-piston NR500 four-stroke and never scored a single point.

Two-strokes make a lot of sense – they are light, compact and very powerful, thanks to producing twice as many power strokes. In Grand Prix trim, 400 horsepower per litre is easily attainable.

That performance does come at a price – an unforgiving power delivery that demands skilful throttle control, which is why many of today’s top racers, Valentino Rossi included, really miss two-strokes. The 500s were motorcycles that didn’t suffer fools. They were at their nastiest in the 1970s and ’80s, before advances in technology exorcised their worst excesses.

Perhaps the most vicious 500 was Honda’s 1989 NSR500, a 190mph weapon with a habit of hurling its riders into the barriers. Four-time 500 champion Eddie Lawson said, “riding the NSR was like death – every time you flicked into a turn you didn’t know if you were going to make it out”. Lawson tamed the NSR to win the ’89 title (above), surely one of the sport’s greatest achievements.

The switch to four-strokes 10 years ago made some sense, since the Japanese were no longer selling two-stroke road bikes. But the move attracted disdain from those hard men who’d mastered the 500s. Asked what he thought of the 990s, Frenchman and former 500 winner Christian Sarron opined: “Zey are okay… for girls.”

The primary reason for the two-stroke’s demise is that in original form it is a dirty engine. Soichiro Honda always hated the so-called ‘stink wheels’, which is why his company was the only Japanese manufacturer that made its name with four-strokes. In recent years Honda has led the way in marginalising the two-stroke.

But modern direct-injection technology can make the engine at least as clean as a four-stroke and several companies are still busy with two-stroke R&D, most notably Lotus Cars whose Omnivore two-stroke with variable compression and trapping valve may just be the future for four-wheelers as well.

In motorcycling, Austrian brand KTM (Europe’s second-biggest bike maker) is the engine’s greatest advocate. “We don’t see the end of the two-stroke – scientific research gives no killer argument,” says KTM race boss Winfried Kerschhaggl. “The decision to get rid of two-strokes is political, the outcome of a brilliant PR campaign by Honda. I have the impression that Honda are trying to change the industry because of their decision to stop making two-strokes. I don’t understand why other Japanese factories follow them.”

Neither do I. Two-strokes once made wonderful road bikes – thanks to an outstanding power-to-weight ratio and lively power delivery – and with direct injection there’s no reason why they shouldn’t again. KTM – fired up by sales of its two-stroke motocross machines – might be the first make in decades to create a high-performance two-stroke road bike. If so, I’ll be first in the queue.