“Birth of the Dragon,” a Bruce Lee biopic*, is set in 1964, two years before “The Green Hornet,” when Lee was an expatriate* martial-arts instructor in San Francisco trying to market himself as a star. He was born in San Francisco but raised in Hong Kong. That year, he had a duel with Wong Jack Man, a Chinese master who showed up to challenge* Lee.

According to the opening title of “Birth of the Dragon,” this single clash would change the entire history of martial arts.

The film’s central character wasn’t even Bruce Lee. It’s Steve McKee (Billy Magnussen), a rube* from Indiana who travels to San Francisco, and winds up passing out*, drunk, in front of the studio where Lee gives his martial-arts classes. Lee takes him in and signs him up, and the two become friendly. It’s Steve who makes himself into the liaison* between Lee and Wong Jack Man (Xia Yu), a disgraced monk from the Shaolin Temple who shows up in a fedora suit and lands a job in Chinatown washing dishes, which is supposed to be his Buddhist penance* for a mysterious sin.

Wong is quite open about his hostility* to the fact that Lee’s students include Caucasians*.

Philip Ng, the Hong Kong-born American actor who plays Lee, has the right face, the right haircut, the right physique — and he’s got a puckish gleam of confidence.

Yet unlike “Dragon: The Bruce Lee Story,” the 1993 Lee biopic, this one keeps hitting you with the Lee “mystique*.”

You wouldn’t even know that he was married, and what he did to get his showbiz career off the ground remains vague.

Finally, he and Wong have their fight. In the film, it happens in a warehouse, and it’s as stylized as any fight in a real Lee film. Who wins? The historical record is a muddle: Some say that the fight lasted for three minutes, others say for 40, and most say Lee won, though that isn’t for sure.

There’s a crime plot (more concoction*), a romance between Steve and the indentured beauty (Qu Jingjing) he tries to rescue from the San Francisco Chinese underworld, and Lee and Wong become teammates in this effort. But what a martial-arts fan really wants to know is: Why, and how, did the legendary 1964 fight between Bruce Lee and Wong Jack Man change Bruce Lee’s fighting style? The film doesn’t give a clue.(SD-Agencies)