"You see things vacationing on a motorcycle in a way that is completely different from any other. In a car, you're always in a compartment, and because you're used to it you don't realise that through that car window everything you see is just more TV. You're a passive observer and it is all moving by you boringly in a frame. On a cycle the frame is gone. You're completely in contact with it all. You're in the scene, not just watching it anymore, and the sense of presence is overwhelming."
Robert M Pirsig, Zen and the Art of Motorcycle Maintenance

It had to be a Harley-Davidson. I don't care for them much normally - big, cumbersome, noisy things with all the disadvantages of motorcycles (you get cold, you might die) and none of the advantages (they're neither fast nor good for weaving in and out of traffic). But to cross America, coast to coast, by any other means would have been ridiculous. Peter Fonda and Dennis Hopper did it on Harleys, so I was going to do it on a Harley, too.

And they have good names: Night Train, Dyna Low Rider, Fatboy, Electra Glide. Mine was a Heritage Softail Classic. Heritage, I imagine, means that this bike has a lot of pedigree. The Softail bit refers to the rear suspension. Classic speaks for itself. I rented it in New Jersey for three weeks, to be returned in Los Angeles.

It was red, and there was a lot of chrome about the place, and black studded leather - nothing like my Vespa at all. For a start, it had a 1,340cc - or bigger than a lot of cars. And I had absolutely no idea how to operate it, but I wasn't going to let them know that. Right, here's a button with "Start" written on it... Brrrmmm. There's that pneumatic drill noise. Now, which way to New York?

That was probably the scariest bit of all, that first ride into Manhattan. Before I had a chance to think about it and do something more sensible, we were out on a highway with an absurd number of lanes. (Note that the bike and I have already become "we".) I was pretty sure we would make a wrong turn somewhere and do a Bonfire of the Vanities. But then we got on to one of those wonderful skyways, and there was Manhattan stretched out in front, glorious in the autumn sunshine. I let out a whoop (the first of many), a mixture of sheer joy and extreme terror.

Twenty days later, we rolled into Los Angeles. Twenty days, 4,283 miles, 13 states, one-and-a-half breakdowns, one wedding (not mine) and one dead chipmunk. I tried to avoid the chipmunk, promise, but like I said, Harleys aren't really bikes for swerving. Oh, and half a suntan - because when you go west for a long time, only the left side of your face gets done.

I'm not sure how it worked out as 4,283 miles (that's London to Delhi, or Chicago even, if you're a crow and you have a lot of stamina). In my Rand McNally Road Atlas, it says New York to Los Angeles is 2,824 miles. We did avoid the interstates, the big multi-laned roads, where possible, and took a few detours. And detours in the US tend to be about 400 miles, generally.

We stayed a day and a night in New York, then set off up the Hudson River - or next to it rather - past Bear Mountain, where Sal Paradise turned back for the first time in On The Road because it was raining. But it wasn't raining, so we kept going, up through New York State with all the trees doing their big fall show-off display. Woodstock for bad art and very good blueberry pancakes, Ithaca for the finger lakes, Niagara Falls for the big waterfall (good, but not as good as the fountain display in front of the Bellagio hotel in Las Vegas). After that, it was pretty much west: Buffalo, Cleveland, Chicago for the wedding. Then the big skies and cornscapes of the Mid-West - like Lincolnshire, except forever. (And there's Lincoln right in the middle, just to prove it.)

Route 66 only exists in parts now, and anyway we were a long way north of it. But we found lots of other good, romantic roads. Like Route 28 through the Catskill Mountains, 92 across the plains of Iowa, or 2 through Nebraska. The road is everything in America; it has a romantic quality you just don't find on the M6. This is because they are much, much longer; you spend a lot more time on them, so they do assume characters. Most states even have an "Adopt a Highway" scheme. In this country, we adopt elephants at the zoo. Americans adopt American roads.

It's a big, old place, the States. I think that really struck me round about Nebraska, probably on Highway 2 - lonely Highway 2 - which meanders through Nebraska's sand hills. This is how lonely Highway 2 is: at the start of the trip I reserved my waves strictly for other Harleys (not so much a wave, actually, more of a subtle gesture with the left hand). But as you get further into the heart of the country, there aren't so many around, so you have to wave at any old bike. And then you start getting roads where even a car or a truck is so rare it deserves a wave. On highway 2, I was waving at trees.

Trees and trains, because Highway 2 runs beside the railroad. Some trains they were, too: 120 wagons of coal coming east from Wyoming. That's a mile long. And they blasted their horns back at me when I waved - that sad noise only American trains do properly. I can't explain how special it is to have a mile-long train say hello to you.

As you get further away from the coast you start to notice stuff - like how the people get friendlier and less attractive. And their jeans fit less well. I discovered the place with the worst fitting jeans in the world: Iowa 80 (named after the state it's in and the road it's on). It's a huge truck stop; a glorious city of arcade games, Wendy's, shops selling soft toys, model cars, games.

We cut a little corner of Wyoming, then Colorado and over the Rockies, and down through the canyons and deserts of the southwest to California.

The southwest was best to ride through - Colorado, Utah, Arizona - where deserted roads twist along the bottom of red canyons, or run straight across big country, scenery you recognise from a thousand films. This was, I realised, what I'd come for. And it was here that I began to understand what Harley- Davidsons are all about. They're the Bentley Continentals of the two-wheeled world. They're not for nipping about town; they're for effortless, comfortable cruising across big countries, preferably America.

In Colorado, I discovered the throttle lock. You pick your favoured engine speed, lock on to it, and then there's nothing to do at all. You can study the map, take photos, or just sit back and watch as America slides under that big, fat, chrome headlamp up front. And in Colorado, you don't need to wear a helmet, so you've got the wind in your hair as well. Truly wonderful. Now, if I'd had an Electra Glide I would have had a cassette player, too, a journey with a soundtrack...

There were lots of good times. Like going over big bridges - it's a wonderful thing to go over a big bridge on a motorcycle. And crossing big rivers, rivers you know all about from school: the Hudson, Mississippi, Missouri, Colorado. We went through bridges, too - little covered ones, in Madison County, Iowa. Yes, those bridges.

Carhenge was a good time - a copy of Stonehenge made from old cars, in a remote cornfield in the panhandle of Nebraska. And Mesa Verde National Park, high up in Colorado, was wonderful, once home to the Anastasia people who lived in towered dwellings in the sides of cliffs. And the Grand Canyon, Bryce Canyon, it goes on.

There was, of course, the odd bad time. Like the girl at the Super 8 motel in Kingston - she was definitely a bad time:

"We're all full."

"Yes, I know. You said. But are there any other motels in Kingston?"

"They're all full."

"Where do you think I might find a motel that isn't full?"

"I don't know."

And so it went on. She was very determined not to pass on any information that might be of any help to me. They weren't all full either. I hope you rot in that reception in Kingston the rest of your life, honey.

The wind in Wyoming was a bad time, too, so strong we had to ride at an angle just to stay upright, if that makes sense. And it was cold at 12,000ft in the Rockies, but we missed the snow by a day and the hot springs at Idaho Springs, on the other side, soon warm you up.

Breaking down on Interstate 80 going into Cleveland started off being bad. There was a popping noise, and we just stopped. Now I'm no expert in the art of motorcycle maintenance, so I just sat there, wondering what the hell to do... for about four minutes: then state patrolman Art Demico showed up in his patrol car and got on the radio. "Got one from London here, and I don't mean London, Ohio." Art also said I should have been on a Honda; where's your patriotism, man?

Within an hour, I was on the back of a tow truck, on the way to South East Harley-Davidson, where I had to say everything twice because the way I spoke cracked them up so much. I was happy to keep them amused so long as they fixed it - an electrical problem they said.

The other half time I broke down was when the starter motor packed up in the Rockies, which just meant I could only stop on slopes until I got it fixed in Vegas. But that wasn't so bad because it's mostly downhill to Vegas.

It got a little lonely at times. I'd done a long motorcycle trip before - Madras to Colchester - but I'd forgotten how little there is to do except think. And sing, but I don't know more than the beginnings of many songs. So I just read the signs by the side of the road: "Re-elect Fox sheriff", "Single-shot training rifles at $59.95" (tempting), "We fought four wars for this land", "The 10 commandments aren't suggestions".

And I like American place names, too. Generally it's obvious how they came about: Muddy Creek, Red Lake, Pleasant View (though Disappointment Valley I thought was wonderful). But you do get the odd one: What Cheer, Normal, Hygiene, Paradox.

I also found the fastest way to dry socks in the world: tie them to the handlebars and drive them at 75mph through the Nevada desert.

I knew my way round Los Angeles before I got there because I'd driven a Harley round it on an arcade game in the Harley-Davidson Café in Las Vegas a couple of days earlier. Interesting that on a day off, while the bike was being fixed, I'd gone to the Harley-Davidson Café and sat at the bar on a Harley-Davidson seat. But it got like that; after a while, you just want to go on and on.

Arriving in LA was exciting and a little sad. Exciting because we'd made it across, and sad because it was all over. We went to see the sea at Santa Monica, just to prove we'd made it all the way across. And then it was like when Dean Moriarty said in On the Road: "We can't go no further 'cause there ain't no more land!"

The practicals

Sam Wollaston hired his bike through Hemmingways (01737 842735, www.hemmingways.uninet.co.uk/) where 21 days' rental costs &#163'1607 exclusive of insurance, drop-off charges and tax. Riders must be at least 21 and have a full bike licence. He flew into New York and out of LA - BA currently has a "value-fare" of £205 plus taxes. Otherwise STA travel (020 7361 6262) has student/under-26 fares of £223 on Virgin, or £239 open to all on United. For guides on the Great Lakes and the Heartland contact Cellnet Travel Services on 01564 794999. For information packs on Las Vegas and Nevada, call 08705 238832.