Eight months ago, MacAskill’s daily routine was fairly predictable. He would leave the apartment he shares with a roommate, hop on his bike and maneuver through strangling traffic to his job as a bicycle mechanic.

Along his route, he passed a metal fence with a spiky top. He had eyed it for years.

“I’d look at it and say, ‘I can ride that rail,’ ”said MacAskill, 24.

He eventually got up the nerve, and the subsequent 30-second trick — which took four days to shoot — became the jaw-dropping highlight of a 5-minute-37-second videoposted on YouTube in April.

The video shows MacAskill on his bike, jumping over fences, walls and other obstacles; doing a back flip off a tree; riding the spiky fence; and performing other hair-raising stunts that could make him the toast of orthopedic surgeons everywhere.

“I am more comfortable on my bike than I am on my feet,” he said.

The video was filmed over six months by his roommate, Dave Sowerby. It made MacAskill an instant inspiration to a generation of young cyclists. With more than 13 million views, it is the Top Favorited sports video in YouTube history, according to the Web site’s statistics.

Within days, MacAskill’s life was upended.

“Everything went crazy,” he recalled recently over a pizza lunch. “I’d get up in the morning and be doing interviews while I was still in bed.”

One day, he was asked to appear in 10 countries. Filmmakers wanted to make documentaries about his life. Advertisers pounced. Big companies, like Red Bull in Britain, lined up to sponsor him. People wanted his autograph. Ellen DeGeneres, who bears a faint resemblance, wanted him to dress up as her and ride around Los Angeles. The Doves, a British rock band, wanted him for a video. Lance Armstrong called MacAskill’s video “a must watch.” A circus in South Korea wanted to hire him to perform stunts.

“It was unmanageable,” he said.

MacAskill took advice from friends and did some commercials but mostly let the offers pile up.

“I didn’t want to grab everything while I could and look like an idiot,” he said.

He took months to find a manager, Tarek Rasouli, a former professional mountain biker whose firm, Rasoulution, is based in Munich.

This was quite a turn of events for MacAskill, who said he rode only for fun and, until he was 18, called his bicycle his best friend. One of six children of a local businessman and an office worker, he grew up in the rural village of Dunvegan on the Isle of Skye. He started riding when he was 4.

“I got my first proper bike at 11 that was a gift from my parents and my aunties,” he said. “I owe them a lot.”

In horizontal rain, cold temperatures and anything else Mother Nature hurled at him, he would ride his bike each day, practicing old tricks and dreaming up new ones.

“I could do the longest wheelie among my friends,” he said.

The police were not amused and frequently cited him for reckless riding, sometimes confiscating his bicycle for weeks.

“I wasn’t an angel, but it was a place where maybe one or two cars would come by every five minutes,” MacAskill said, and that was during rush hour.

Hindered by dyslexia, he left school at 17 and moved to a resort town in the Scottish Highlands.

“My goal in life was to work at Bothy Bikes in Aviemore,” MacAskill said. He stayed there and lived under the watchful eye of his aunt Jean Hamilton.

“He was always a risk-taker, much to my horror,” Hamilton said. “As a family, we like to feel he wouldn’t try anything that would kill him.”

As he had on Skye, MacAskill would turn up at cycling shows and demonstrations in the Highlands. Trials riding, with elements of extreme cycling and mountain biking, is a small sport with a passionate following. Cyclists maneuver over obstacles with nothing touching the ground but their tires. MacAskill has been credited with carving a niche called street trials riding because he cycles in urban locations and has added tricks to his repertory.

As his reputation grew, offers from cycling event organizers began to roll in.

Three years ago, in search of bigger challenges, he moved to Edinburgh and took a mechanic’s job, this one at MacDonald Cycles, the store whose roof he leapt onto in the popular video.

He built his 24-inch stunt bicycle with components from an assortment of A-list parts makers and frames supplied by Inspired Bicycles, an English firm specializing in mountain bikes. Inspired’s founder, Dave Cleaver, was an early supporter of MacAskill’s and posted the video on YouTube. His company recently unveiled two models similar to the bikes MacAskill rides, which cost about £1,300 (about $2,080).

After MacAskill made an appearance in early 2008 in Birmingham, England, he and his friend Iain Withers formed the Clan, an all-Scottish stunt cycle team that began performing at trade shows, events and schools.

“There was enough interest in what we did that I realized for the first time I could ride my bike for a living,” MacAskill said.

Withers said he knew of MacAskill but did not see him in action until 2007.

“I’d heard about this awesome kid from the Highlands,” Withers said. “From the first shows we did, it was clear he had a totally different attitude toward what was possible on a bicycle.”