The young cyclists, three Britons and an Irishman, had quit their jobs and come to this country to raise money for the victims of the 1985 Mexico City earthquake.

What they discovered was the real world of professional charity.

Even though they had netted $40,000 in England with a benefit concert by Placido Domingo, American fund-raising organizations tended to view them as invaders of their turf.

And then, three months and 4,000 miles later, they said, the Mexican Embassy told them that it needed no more help, that the earthquake victims were all taken care of.

And one of them, disheartened by personal frictions and endless days of biking through the rain, quit and went home.

"But things are looking up now," said Adam Baines. "We've got our act together and we're moving ahead. We've made a pledge: We're not stopping until we've raised $50,000."

It was Baines, a 27-year-old London advertising executive and Oxford graduate, who had the idea for Operation Mexico. "Last December," he said, "I read a story in the Observer about the quake, about how there were still 100,000 people living in the streets of Mexico City, 60,000 children. I went to several charity organizations, but they weren't interested. Then Save the Children said they could help."

He ran an ad for recruits, got 50 replies, picked two young Englishwomen and an Irish folk singer who also happened to be an engineer with experience in community housing.

In six months the team, with the enthusiastic aid of Domingo, put together the concert, a benefit ball and a spectacular stunt in which the famed singer rode an actual bike in a sort of living billboard high above a busy London street.

The group knew that the public attention span is about the same as that of a 12-week-old puppy, that the Mexico City quake was long forgotten. But they learned that the public can, after all, be reminded.

"Domingo wrote a letter that was handed out with the tickets to his Covent Garden concert," Baines said, "and we raised more than $2,000 from that one thing. You remind people and they say, Wow, yes, I remember that one, yes, and the money comes in. A big corporation can't do that. Its priorities are fixed. But we realized that ordinary people were the answer."

So last July they landed in America, with high hopes and brand new bikes donated by Raleigh. They were going to ride from Maine to Mexico, raising $50,000 along the way. Baines and Chloe Thomas, 28, the one Spanish-speaking member, arrived first, soon followed by Deborah Green, 22, who started late because she was graduating from Oxford Polytechnic University, and Alan O'Donnell, 30.

They were to rendezvous at Eastport, Maine.

"We weren't cyclists," O'Donnell said. "It was our first time on loaded bikes. We didn't know the roads, it was a strange country, and we got lost in the night. We got to the post office about 9 p.m. and found a note stuck to the door, and eventually we all met in a bar down the road. Well, the bar people heard our story, and got us on local TV, and had a busload of 50 kids to see us off next day with some donations and a lobster breakfast."

The plan was to contact opera people in various towns and organize little concerts, then build publicity any way they could. Already they were writing ahead to sources in New York for a huge production.

But first they had to learn about bikes.

"None of us had cycled more than a few miles at a time," Baines said. "We didn't know how to stay together, and the very second day we got lost. Then things started to go wrong with the bikes. And we were sore!"

Arriving in Boston, the group organized a huge bicycle contest. They would race bikes against taxis, against streetcars. They would show that bikes can cross a city faster than anything.

"We got the police cooperating, and City Hall. We had radio spots. We put our posters in every bike shop in town and alerted every cycling club. A great reception was organized, and everything."

They thought hundreds of cyclists would respond, each paying the $10 donation fee.

One cyclist showed up.

Three weeks later, after any number of minor accidents involving cars, pedestrians and dogs, they reached Westport, Conn., home of Save the Children. There they learned about the fund-raising business. The people were friendly, but Operation Mexico's track record in England meant nothing here. Theirs was just another possible project. Save the Children had its own priorities, its own plans.

"So we had to prove ourselves," Baines said. "Rosario Andrade, a prote'ge' of Domingo, was to sing for us in New York. We found a big studio for the concert, a Mexican restaurant donated food, Bacardi donated liquor, we had it all. It was a lovely evening, everything worked ... but we just didn't get the crowd we needed. The ones with money."

They learned that publicity can't be rushed, that it takes six or eight weeks to build a major event.

They also learned that people do give.

"We stopped in New Hope, Pa., and Lambertville, N.J., just across the river," O'Donnell recalled, "and we just went up and down the street, stopped at 60 stores, talked to people. In three hours we made $300."

Faced with their energy and commitment, people emptied their pockets. The local newspaper wrote them up, so that even after they had left town, readers could see that "we were for real, that the Mexican earthquake wasn't forgotten, that people have given up their jobs to do this."

When they reached Washington last week, they found a welcome at the Save the Children office on Connecticut Avenue. The women there loaned them office space, phones, copiers and support. The bikers rustled up free lodging for a stay of several weeks while they settled down to organize a giant event in town.

"We're not trying to save the world," O'Donnell said. "We are taking part in a very specific project by the Save the Children counterpart in Mexico -- to complete an 80-house development in Mexico City that is still 20 houses and $100,000 short. It's a self-help program, training people in construction as it goes. So far we've raised about half of that, and we have $50,000 to go."

They understand now about fund-raising turf: There are only so many dollars waiting to be donated. They understand they are backing a half-forgotten cause. They understand why the Mexican government is not embracing them. ("The damage is 98 percent rebuilt," said deputy press attache' Enrique Verruga at the Mexican Embassy. "The people have been taken care of, relocated, given special rehabilitation. If those cyclists' figures about 60,000 children still being homeless two years after the quake were true, what sort of nation would we be? Why, we'd be on the brink of revolution.")

"But the things that have happened, you wouldn't believe it," O'Donnell said. "We were passing by the Berlitz office on Connecticut the other day, and we were worried because we'd lost Chloe, our Spanish speaker, and none of us spoke a word of Spanish. So we went in, all in our gear, and talked to the manager."

The manager, William Kraus, was so enraptured that he literally turned out his pockets to give them the money he had on him.

And the next morning he phoned them. He had arranged a free Spanish course for them.

"I could talk for hours about the nice things that have happened," Baines said. "We've been on the road eight weeks and haven't had to pay for accommodations once. We only used the tents seven times. People have fed us, given us clothes, food, so many things we're simply loaded down, we can't carry any more."

A woman named Virginia met them in a small town in Maine, promised to get them some contact names and numbers, went home for her address book, spent the whole day driving around to find them again.

Someone loaned them a car for a while just so they could ride into town in comfort.

O'Donnell, delayed by bike trouble, was given a lift on a fire engine, pursued the others for 80 miles to catch up.

In the Amish country, a man dragged them into a restaurant and bought them an enormous pizza and all the beer they could manage.

Even in New York, as they sat watching the Harmonic Convergence rally, a reporter from the Financial Times got to talking with them and they wound up spending the night in his apartment. He put them into his story about the rally.

And the Mexican consul in that big, tough city took 100 of the Operation Mexico T-shirts they'd had stenciled on someone's advice in Maine, and sold them, and handed over $1,000.

On the road, they average 50 miles a day. They are so acclimated to their bikes that "none of us has walked 100 yards in the last two months." They love meeting other cyclists at stoplights, talking shop: small flange or big flange, the wear on the front tires, the brand names. They figure none of them will ever be quite the same again.

Each of them saved $1,500 for the trip, borrowing from friends, selling their cars, whatever it took. They planned on spending $15 a day each, and not surprisingly they are running low on cash now.

After putting on their event in Washington -- still in the hush-hush stage -- they will hit the road again, though they probably won't leave the United States after all.

They will keep going as long as it takes.

"Disrupting my life?" said Adam Baines. He smiled. "This is my life."