The race was supposed to be Bill Warner's last. The fastest man in the world on a motorcycle — the only one to reach an incomprehensible 300 mph — was set to leave the sport with a new record.Mr. Warner, who paid the bills with his fish farm in Wimauma, wanted to open a race track in Houston. But there was one more hurdle left, and it came on Sunday at Loring Air Force Base in Limestone, Maine.For several years, he had just one challenger to defeat: himself. In 2011, Mr. Warner rode his turbocharged Suzuki Hayabusa to a world record of 311.945 mph within a mile and a half.It wasn't enough. Before retiring, Mr. Warner wanted to break 300 within one mile.He was already a legend. The inner-circle world of motorcycle racing, in which close friends live hundreds of miles apart and reconnect at a handful of former airfields or the Bonneville Salt Flats in Utah, was well aware of Mr. Warner's ridiculous feats."He's got the next fastest guy beat by like 40 mph," said Steve Knecum, a former rival who once held the world motorcycle record himself. He later built Mr. Warner's supercharged engines."I relate it to baseball," said Larry Forstall, a former top rider who broke 200 mph himself. "If you hit .300, you're a star. And he was hitting .500."He was that much better than everybody else."The startling fact, one some grizzled riders found hard to accept: Apart from a little dirt biking in his youth and the most casual kind of experience as a motorcycle owner, Mr. Warner had virtually no experience with racing until eight or so years ago.The vast majority of people who race motorcycles do not do it for the money — there isn't any. If anything, they need help from sponsors to pay for gas and lodging around the country.Two-wheeled speed demons have been gathering at Bonneville for 60 years, said Forstall, 70, who has made the trip 32 times. They rode "conventional," or open-wheeled motorcycles.They have raced on former air strips in Moultrie, Ga., where the East Coast Timing Association was formed in 1995; then in places like Maxton, N.C. and Wilmington, Ohio.They competed against each other but also against even the mildest wind that could put them on the ground and the mechanics of vehicles not designed for these speeds. Mr. Warner contended with blistered tires, a blown transmission during a race and two previous crashes. One put him in the hospital for a month."You have to really want to do it," Forstall said. "It's not golf. It has consequences."William Warner was born in 1969. He grew up in Little Falls, N.Y., and wrestled for his high school. According to his Facebook page, he moved to Hillsborough County and studied marine biology and chemistry at the University of Tampa.He was confident but not cocky, friends said, an unassuming man who wore a baseball cap and shorts everywhere.For a while, he worked at SeaWorld as a marine biologist, crew chief Bob Sellers said. He never married but had a girlfriend."He was a scientist," said Sellers, 57. "They call him a mad scientist."In the early 2000s, Mr. Warner bought a Yamaha V-Max. When it was noted that it could not go 200 mph — something no other showroom motorcycle could do either — Sellers said Mr. Warner asked him, "Why don't we build one that can?""You don't use the word 'can't' with Bill Warner," Sellers said.Soon Mr. Warner was racing, tinkering and adjusting."It was like lightning," said Forstall, a friend and mentor. "We had never seen anybody go from just starting out to being the best in the world."Mr. Warner bought a Suzuki Hayabusa and rode it to a world-record 278.6 mph in 2010.To go faster, he got a second Hayabusa and modified it to take methanol, or wood alcohol.He set the world record two years ago, going from a dead stop to 311 mph in a distance of just a mile and a half."Even I have a hard time comprehending it," Forstall said.Now he wanted to crack 300 in just a mile. But as his speeds increased, Mr. Warner had a bit of trouble: the front wheel tended to lift off the ground as he hit 280 to 285 mph."It scared the hell out of him," Sellers said, "and it would scare any human being on earth."The bike seemed to be performing well Sunday. Before a crowd of about 500 at the Maine Event, an annual race sanctioned by the Loring Timing Association, Mr. Warner had made three runs — including a world-record 296 mph.His fourth try could not have started out better."It was faster than the word of God," Sellers said. "The tires squealed, it fishtailed, the back of the bike swung left and right and he was gone. If you had looked at me and turned back for a second, you couldn't find him."At the mile point, Mr. Warner was clocked at 285. Then something went wrong.His motorcycle drifted to the right and hit a concrete barrier. The bike exploded. Mr. Warner flew some 900 feet, according to news accounts.He died an hour later. Mr. Warner was 44. He is survived by his mother, sister and brother.Track officials told the Bangor Daily News that they, and Mr. Warner, maintained the highest safety standards. The cause of the crash is unknown."Everybody is trying to sort it out," Forstall said. "But it doesn't matter because we lost him."I don't think there will be anybody to follow in my lifetime what he's done."Andrew Meacham can be reached at [email protected] or (727) 892-2248.