LET'S GET A FEW things straight right at the start. First of all, motorcycling is dangerous. It combines the fragility of bicycling with the destructiveness of speed. Second, motorcycling appeals to adolescent urges. Men who ride these macho machines after the age of 19 are probably experiencing protracted midlife crisis and should be ignored until they get over it.

Third, motorcycling is irritating to everyone who is not on the motorcycle.

Yet there are nearly 7 million people riding motorcycles in America, 95 percent of them males. Last year, more than 800,000 new bikes were sold, and the bulk of the market isn't kids looking for thrills, but men 30 and older -- baby boomers with money.

What is the mystique? What compels those of otherwise sound mind to expose themselves to the unforgiving perils of careless auto drivers and solid asphalt, on machines that offer no protection and are made to fall over if not properly ridden?

"Freedom and the feeling of release," says Jim Vance (Harley-Davidson Wide Glide), WRC-TV anchor.

"The action, speed, beauty, excitement and the feeling of being in control," says Peter DeVito (Yamaha 920 Virago), an advertising salesman for U.S. News & World Report.

"When you ride, your senses are literally bristling," says Denis Rouse (BMW R100), publisher of Rider, a magazine of motorcycle touring. "I remember every detail of everywhere I've been on a motorcycle."

"On a motorcycle," says conservative millionaire businessman Malcolm Forbes, who owns 45 bikes, "you're tuned in to all the fundamental elements of nature. You have a total new awareness of weather and the world around you. It's a refreshing experience."

These men are all successful professionals more than 40 years old. Two of them never sat on a bike in their early years; Jim Vance first took up riding at 41, Malcolm Forbes at 48. Nevertheless, many of today's motorcycle buyers are what John Row, advertising manager of American Honda Motor Co. Inc., calls "born-again bikers -- men who gave up motorcycles when they got married, then went through household building and just had no room in their lives for a motorcycle. Now they want to get back in. We say, 'Once hooked, always hooked.'

Hooked is right. I gave up motorcycling after a memorable trip across Europe on an old single-cylinder BMW 250 when I was in college; it was another 15 years before I again set boot to bike and discovered the revolution wrought by Soichiro Honda and the rest of the Japanese motorcycle industry. What was once a very hard labor of love, I discovered, had become a high-tech luxury.

The scales fell from my eyes on the day I picked up a 1978 Suzuki GS750. I knew you could now start the things with a button, instead of six kicks against high compression. I could see that they had turn signals and soft saddles and halogen headlights. But I could not see what engineers had done with the inside of the motor. What had years before been a shaking, leaking single-cyclinder heap was now a finely tuned four-cylinder power plant; it was like riding greased silk with your choice of rocket engines. I never wanted to get off.

TODAY MY MOTORCYCLE is obsolete. Since 1978, the Japanese motorcycle men have produced quantum breakthroughs in performance. One recent weekend, I rode 400 miles on a 1985 caf,e racer from Japan that appears to be going fast even when it is parked. Its handling, road presence and ready power are astounding. It accelerates like a starship leaping into hyperspace.

But it's not only the new wave of hyperbikes that are keeping reborn motorcyclists coming back by the several hundred thousand per year. There are also stylish black cruisers that rumble along the boulevards competing for macho with throaty, low-slung Harleys. There are even plush $10,000 touring machines that resemble motor homes on two wheels, with digital speedometers and stereo systems like your living room's. All the fancy hardware only serves to enhance the allure: freedom and control.

MOTORCYCLING brings a sense of escape other men may find through sailing, flying, hiking, skiing or mountain-climbing. Yet motorcycling is so much more immediate and available. A simple 20-minute run up the George Washington Parkway along the Potomac River clears the senses and the sinuses. There is speed, power, mechanical harmony. Highway seams and roadbed undulations become palpable, almost athletic sensations, like whitecaps slapping the hull of a small, fast sailboat.

Most of all, there is a feeling of liberation; I am completely in charge of my space. With a simple twist of the throttle grip, I leap miles and mindsets away from the fetters of daily life. The 20-minute ride can becama 150- mile roll and I'll still be home in time for dinner. Just being on the road with the wind's roar in my helmet puts me on the edge of escape.

On a motorcycle, you ride close to nature. Roadside flowers seem within arm's reach; bugs spatter on your arms and face shield. Weather is sensed before it happens; an impending thunderstorm is felt before seen, the rider heading away, finding new sun.

Twenty years ago, Robert Persig noted the special appeal of being in touch with the earth while moving through it at speed in the opening passages of his classic Zen and the Art of Motorcycle Maintenance: "In a car, you're always in a compartment . . . 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. . . . the sense of presence is overwhelming."

Like a Wednesday night poker game, motorcycling is also a vehicle of male bonding. A couple of years ago, I rode 2,500 miles through New York and New England with a group of three-piece-suiters. The American president of Saab was there, along with a vice president of Sony. There were several advertising types and a couple of brothers who owned their own sheet metal company. In real life, these men are all pillars of family and community. But, like Clark Kents in phone booths, they occasionally strip themselves of domestic trappings and become a leather-jacketed motorcycle club called, mock-heroically, the Sons of Danger. Riding with these unbuttoned businessmen induced a great sense of open-ended camaraderie, like latter-day cowboys out on a long-range ride.

Motorcycling can enhance other kinds of bonds as well. Bob Sinclair, president of Saab-Scania, can get Swedish cars anywhere but prefers motorcycles in his free time; he keeps one on either coast and calls friends at BMW when he needs one in Europe. At 50, Sinclair reconnected with his daughter through motorcycling.

"She was off at college, but we had more or less lost touch when she was a teen-ager," he says. "I finally decided, I'm just going to take a week out to be with her. We took an 850-mile ride from San Jose to Yosemite and along the Gold Rush route. It was a marvelous trip. We slept by streams and bathed in nature. We found a communality of interests. And the motorcycle was the device that brought us together."

Sinclair's daughter is one of thousands of women who ride motorcycles of their own. These women often cite the same reasons men give for riding -- freedom, independence. Pat Shema (Yamaha 650 Maxim), a veterinarian in Lanham says, "When I ride, I have complete control. I can escape the pressures of the job to think and be alone in nature."

For some women, motorcycling initially presents a gender obstacle. "I always felt it was a man's sport that I would never be able to do," says Paula Matthews (Honda Shadow 500), a secretary at American Honda. "I worked here for four years before I tried a motorcycle. Now I love it. I feel a lot more independent, knowing I can ride."

Clearly, motorcycling has more demographic dimensions than meet the public's eye. The motorcyclist most often seen by the average citizen may be young, reckless and arrogant. He favors loud exhausts, rides without a helmet and looks as if he eats babies for breakfast. Yet the other world of motorcycling includes fortyish executives who ride on weekends and mom-and-pop retirees who ride two-up all across the country with saddlebags and CB radios. The dean of respectability in American motorcycling comes in the unlikely form of magazine publisher Forbes, who occasionally hosts parties for Washington's power elite aboard his 126-foot yacht, Highlander. Forbes discovered motor- cycling when his chauffeur asked for a loan to buy one. He at first refused the loan, then re- lented and made the mistake of riding the new machine. "It was fun," he says. "Pretty soon I had my own bike."

Forbes was never a man to deny himself a pleasure identified; now 65, he has motor- cycled on every continent and recently presented a TV special about his trip on a Harley-Davidson through China. Last year Forbes had a major spill while riding in Glacier National Park. "I took a curve too fast and hit gravel," he says. The accident caused Forbes a punctured lung, broken ribs and a concussion. Today he is riding again, and he can explain why:

"I used to think people who rode motorcycles had a screw loose. But the public image of motorcycling is all wrong. The bad guys are the exception, not the rule. What people don't understand is that motorcycles are not dangerous. I mean, they are dangerous, but you compensate by being infinitely more aware, more alert, more careful. You're more anticipatory of what others are doing."

To say that motorcycling is not angerous seems ludicrous to those who have been maimed or lost loved ones on bikes. Controversy rages over helmet laws and 125-horsepower engines. The greatest single problem in riding remains the apparent inability of motorists to treat a narrow-profile, two- wheeled machine with the same respect they give automobiles. The majority of fatal accidents involve a car pulling inadvertently into the path of a motorcycle.

Motorcycling is not for everyone. New riders are strongly advised to take a course sponsored by the Motorcycle Safety Founda- tion, since proper handling of a 500-pound powerhouse requires a new set of skills.

But for those who ride, motorcycling can bring a unique joy. Says Mike Ashford (Harley-Davidson Super Glide), an Eastern Airlines pilot and proprietor of McGarvey's saloon in Annapolis, "Just booming along the road dumps a whole lot of life's little problems. Sometimes without realizing it, I'll notice I'm all of a sudden grinning to myself inside the helmet."