Interesting. I always thought Steve McQueen did the jump himself.

San Antonio Express-News 10-10-07:

Stuntman of ‘Great Escape' fame
dies at age 77 of natural causes

Ekins doubled for actor McQueen during film's motorcycle jump.

DENNIS MCLELLAN
LOS ANGELES TIMES
LOS ANGELES — Bud Ekins, a pioneering champion off-road motorcyclist and a veteran stuntman who doubled for Steve McQueen on the famous motorcycle jump in “The Great Escape,” has died.
He was 77.
Ekins died Saturday of natural causes at Cedars-Sinai Medical Center in Los Angeles, publicist Paul Bloch said.
A 1999 inductee of the Motorcycle Hall of Fame, Ekins was one of the first Americans to compete in the World Championship Motocross Grand Prix circuit in Europe during the 1950s.
By the middle of that decade, he was the top scrambles and desert rider in Southern California and had been district champion seven times.
His friendship with fellow motorcyclist McQueen, whom he helped teach off-road racing, launched Ekins' career as a movie stuntman.
He amassed numerous stunt credits, but his most famous stunt work was on his first job: doubling for McQueen in the climactic motorcycle jump over a high, barbed-wire fence in the 1963 World War II prisoner-of-war movie “The Great Escape.”
“Steve could have done it himself,” said Bob Hoy, a stuntman friend of Ekins. “He did the lead-up to it and rode the bike wherever he was running in that escape, but Bud did the jump. It was a tough jump. You only can do that kind of thing once; you either make it or you don't make it.”
Susan Ekins, Ekins' daughter and an executive film producer, said her father was “very proud” of the spectacular jump, which was shot on location in Germany.
She said her father and McQueen dug out a ramp in the dirt, and they both practiced jumping the motorcycle over a rope to see if it would be able to clear the fence.
“Steve was a very capable rider, but my dad did the jump because they wouldn't let a star do a jump of that nature because they couldn't afford to have him hurt,” she said.
Producer Jerry Weintraub, who knew Ekins for 30 years described him as “a man's man.”
“He taught most of the movie stars in this town how to ride motorcycles,” Weintraub said. “If somebody wanted to buy a great motorcycle ..... they'd go to Bud Ekins. He was an icon.”