When the comedian Robin Williams heard in 2008 that world-renowned Italian handmade-bicycle builder Dario Pegoretti was in the United States for the North American Handmade Bicycle Show, he flew on his private jet from his home in Tiburon, Calif., to the show in Portland, Ore.

Williams owned possibly the world’s biggest collection of bicycles by Mr. Pegoretti, who died Aug. 23 in Verona, Italy, of a heart ailment at 62.

Williams, who considered cycling “mobile meditation,” liked to give Mr. Pegoretti’s bicycles as gifts and wanted to meet the man who had built them. They became close friends, and at that Portland show, Mr. Pegoretti was named frame builder of the year, one of the highest accolades in the business.

After Williams took his own life in 2014, columnist Jason Gay wrote in the Wall Street Journal that “what Jay Leno does with cars, Williams did with bikes.” In 2016, Williams’s family, per his request, held an online charity auction of 87 of his classic bikes. One of his Pegorettis, a Responsorium model, sold for $22,000, a highlight of a sale that raised $600,000, according to the New York auction house Paddle8.

Having built bikes for four decades, Mr. Pegoretti became internationally known among bicycle connoisseurs who considered him not just a great craftsman but an artist.

The craft was in his steel-and-aluminum, lugless welded frames, which he innovated and stuck with after most sport- and racing-bike builders began using carbon fiber. Bikes had traditionally been built using steel tubing with socket-like sleeves, called lugs, to connect the tubes. Mr. Pegoretti instead used tungsten inert gas welding, or TIG, to make perfectly smooth joints.

The art was in his painting of the frames, which often featured quotations or images from artists ranging from Jean-Michel Basquiat to Frank Zappa.

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The last all-steel-framed bike to win the most famous race in the world, the Tour de France, was built by Mr. Pegoretti, although it was badged as a Pinarello because he was under contract with that noted company of bike builders at the time. (It was then a common practice for the big builders to use small but respected artisans to make their frames on contract.)

The Spaniard Miguel Indurain, racing for the Banesto team, rode Mr. Pegoretti’s Pinarello frames to victory in 1993 and 1994. The frames were specially built to fit his 6-foot-2-inch height.

Other great racers who rode Pegoretti-built bikes included Italian mountain specialist Marco Pantani, Italian sprint specialist Mario Cipollini and Irishman Stephen Roche, who won the Tour de France and the Giro d’Italia in 1987. Today, a newly built Pegoretti Marcelo model might cost close to $12,000.

Dario Pegoretti was born Jan. 18, 1956, in Trento, Italy, in the foothills of the Dolomite mountains not far from the Austrian border.

He was 19 when he dropped out of his university to become an apprentice under the master frame builder Luigino Milani in the town of Illasi, near Verona. Mr. Pegoretti’s work came to the notice of Pinarello, and he went on to build many bikes used by its professional racers before going into business by himself.

His first studio, near Trento, was in a farmyard before he moved to a former paper warehouse in the town of Caldonazzo. He would finally settle in a studio in Verona, close to where he started.

His business suffered with the rise in carbon fiber and titanium just before the turn of the millennium, but a boost came in the early 1990s when Giorgio Andretta, the Italian American owner of Gita Sporting Goods of Charlotte, began importing and selling Pegoretti bikes in the United States.

They took off among enthusiasts, who began calling themselves Peg Heads.

“I will never be able to afford a Ferrari or a Patek Philippe or a Picasso,” Gordon Haber, owner of Lakeside Bicycles in Lake Oswego, Ore., wrote in a tribute shortly before Mr. Pegoretti’s death. “I own and ride a Pegoretti frame. . . . If you don’t own one, you are living a life of needless cycling deprivation.”

Mr. Pegoretti had been diagnosed with lymphoma in 2007, but he overcame the illness. His son Andrea Pegoretti, who along with his father’s longtime assistant Pietro Pietricola is helping continue the business, confirmed his death. A complete list of survivors was not immediately available.

Mr. Pegoretti’s hand-painted finish, often inspired by music, was widely celebrated. He recalled a musician who sent him a frame to paint.

“He asked if I could listen to his music whilst I painted it, to get inspired,” Mr. Pegoretti told the British website Always Riding last year. “Well, it was heavy metal, so I painted it totally black and sent it back to him. I think he liked it!”