Harley-Davidson's new engine: The great American classic is reborn

Harley-Davidson has done the impossible; turned the pig that was a Hog into a smooth-riding and handling modern motorbike without losing one jot of what makes it special. Tim Luckhurst saddles up

The way Harley-Davidson likes to tell it, there is nothing on two wheels that compares with one of its motorcycles. Other manufacturers build machines; HD crafts lovingly conceived works of art which engage the rider's heart and soul.

To the faithful these truths are self-evident, but in recent years the faithful have not been quite numerous enough. There is no crisis; HD's UK sales rose by 10 per cent last year. But the competition is getting hotter.

According to HD's figures, Triumph, the resurgent British manufacturer, seized 13.6 per cent of the UK market for new motorcycles in 2005, against HD's 12 per cent. Triumph's figures show a bigger lead. That tells a story. Many riders cherish the retro look and feel HD pioneered, but others, including Triumph and Ducati, have been quicker to blend heritage appearance with modern performance.

This has always been within HD's capabilities. It is wrong to imagine that the traditional air-cooled V-twin engines fitted to all except its V-Rod bikes are antediluvian. The sound and appearance are kept traditional because that is what Harley owners want. But the technology deployed to make it durable and efficient is state-of-the-art. That is one reason why Harley-Davidson motorcycles have such exceptional resale values.

Still, by last year the aircooled range was beginning to feel tired, lumbering and middle-aged: fine on wide, straight American highways but utterly un-thrilling on tighter British or continental roads.

Now, engineering innovation has changed all that, pushing traditional design to a new level of performance. At the beating heart of this is a new 1,584cc engine that replaces the traditional 1,450cc plant on three of HD's five families of motorcycles: the Softail, Dyna and Touring ranges, which include such iconic bikes as the FLSTF Fat Boy, FXDB Dyna Street Bob and FLHTCU Ultra Glide.

If you find HD's alphabet soup confusing, don't blame yourself. It is designed to appeal to the sort of American depicted in King of the Hill, Greg Daniels' and Mike Judge's cartoon fable about a pedantic propane salesman. The point is simple - with the exception of the entry level Sportster range and the ultra-modern, watercooled Porsche-designed V-Rods, all Harley-Davidsons have a new engine.

It is very good, delivering more power and torque where a real rider needs it and doing both with greatly enhanced smoothness. The capacity gain has been achieved by lengthening the piston stroke - which might be expected to create additional vibration. It doesn't; for the first time in recent memory, trad-looking Harley-Davidsons feel almost as good as they sound.

The second new addition is an ultra-high sixth gear intended to reduce engine revs when cruising at speed. My response was ambivalent. At 80mph and above, the new ratio leaves the engine feeling fantastically laid back but still responsive. I can imagine relishing it on long motorway journeys. But very few of these machines are ever going to get that sort of use.

Veteran tourers who plan to upgrade high-mileage HD Electra Glide and Road King models will thus be charmed. The new versions of these familiar globetrotting steeds just gained better acceleration, improved passing performance and smoother all-day cruising capacity. But on the naked Softail and Dyna ranges the point of the sixth gear is harder to fathom. It works perfectly, but I fear it will rarely be engaged.

HD takes great pleasure in the new sixth-gear indicator fitted on the instrument panels. It is a small green light that illuminates to remind you that you are in top. It is futile. You cannot fail to notice the feel of so high a ratio. A comprehensive gear-position indicator would be more useful.

The company also waxes lyrical about a new active intake and exhaust system. It works, keeping the 2007 HDs within the latest EU noise and emission limits without damaging the sumptuous Harley rumble. The bikes still sound pleasantly distinctive. But the real gain is to mass production, not to the consumer; the technology can be instantly adapted to any set of emissions standards anywhere. It is a triumph of necessity, not aesthetics - but elegantly accomplished.

More pleasing is a wonderfully simple security system that arms and disarms automatically according to the proximity of the key fob. I loved it. Take the key with you when you dismount, and your Harley is immobilised. You cannot embarrass yourself by setting off the alarm: walking towards the bike switches it off. It is the motorcycling equivalent of the standard American fridge - absolutely fit for purpose.

That description is appropriate for all the 2007 Harley-Davidsons. A beautiful but tired range has been given a thorough technological overhaul. It does not turn sedate cruisers into MotoGP racers, but it has made these American classics a lot more practical. The price of looking cool no longer involves horrendous compromises on performance and handling.

Two bikes stand out. The FXDB Dyna Street Bob, about which I enthused last year in its original 1,450cc guise, was already a fun motorcycle. Named after the stripped-down street racers made from adapted Second World War technology, it exuded nostalgia in a package designed to attract younger riders. It worked; the Bob was HD's biggest UK seller last year. The new version is even better and an affordable £9.095.

More expensive by £4,000 but further improved is the latest manifestation of the legendary FLSTF Fat Boy. Redesigned, with an enlarged 200mm rear tyre and cast aluminium disc wheels, it looks clean and chic. It handles, too; I chucked mine around until footpegs ground against tar. .

Owning a Harley-Davidson has always been a lifestyle choice. You cannot buy these machines for performance alone. But if you adore Harley style, the new range embraces a level of comfort and practicality that was absent and adds enough speed and agility to thrill as well. These machines are not expensive ornaments. They go beautifully too. HD is fighting back.