Whatever you think of the politics of Che Guevara or the bullet that ended his life at the age of 39 in a Bolivian hut, you'll probably be charmed by "The Motorcycle Diaries." That's because it's less an evocation of Che the man than of Youth the experience.

When you were one and twenty, you heard a wise man say, give pounds and crowns and guineas, but not your heart away. Fat chance. In 1952, Ernesto Guevara de la Serna, a med student from a prosperous bourgeois family in Buenos Aires, gave his away, although he was a little old at the time, being 23. He gave it to . . . well, to the wretched of the Earth, the drifting peasants, the beaten-down miners, the dispossessed Indians, the fingerless lepers of his continent.

The film, directed by Walter Salles, chronicles a 9,000-mile journey Che -- then called Ernesto by everyone, as the Che nickname, derived from Argentinean slang, had not yet been coined -- took a trek with a pal across South America. They went on this journey for the reasons most students go to Florida over spring break, having more to do with booze and babes and the first experience of freedom than economic principles. They appear not to have gotten laid. (It was different in the '50s.) But what they discovered was a world of pain. It changed Che forever.

Or did it? Hmmm, that's the problem. It's always tempting to ascribe -- as Salles does here -- the uniqueness of a remarkable individual to a single experience, in which all wisdom is revealed and his life is turned around. That makes a better story, too, and that's the one Salles has chosen to tell, of the implicit radicalization of this mild, handsome, asthmatic medical student with delicate hands and sensitive eyes. We are left with the impression that because he saw the nuns' cruelty to the lepers and the mine foremen's cruelty to the miners that he became a revolutionary fighter, a hero, an executioner and a myth.

This is similar to the explanation of criminality favored in movies and other pop culture narratives -- child abuse, that most melancholy of all crimes against humanity, turns the child into a monster, turns little Hanny L. into Hannibal the Cannibal. But what such single-cause explanations always neglect to mention is that hundreds, thousands, hundreds of thousands of people undergo the same abuse or eye-opening to the world of hurt. Then they come back and get jobs with insurance companies. Or they bury the anger in a faraway place and just go on and live their lives.

The question then that Salles never answers and perhaps can never answer is, Why Che? What drove this mild, physically unimpressive man to put himself in the crucible over and over, even after endless disappointments? What drove him to fight in Guatemala, Cuba, Africa and finally Bolivia? The movie has no clue whatsoever, beyond the generic. Its adherence to the nurture-over-nature theory of human behavior never begins to convince.

So possibly it's best to subtract Che the revolutionary from "Motorcycle Diaries" and instead enjoy the movie as a mild travelogue with sharp characterizations and a human heart, and forget what happened in Cuba in 1959 and Bolivia in 1969.

As Salles has it, from Guevara's own diary and a later book of recollections authored by his chum Alberto Granada, the two set out on the Mighty One, their overwrought name for a seen-too-many-miles American Norton motorcycle, and headed toward the horizon. A year later they had traveled up, down and around, and Salles is very good in capturing the ordeal of the trip.

The 'cycle, for example, comes to have not just weight and power but also a contrary personality. It's a huge, sloppy beast, like a bitter draft horse close to the glue factory, and it's continually dumping them in puddles or ditches. It's always on the verge of letting them down, too, a treacherous, vindictive monster of a machine. Salles gets so much out of its tendency to slither out of control, to ram the occasional cow, to rip tons of dust from the earth or to simply fall apart. Meanwhile, almost like Greek heroes facing Persians or St. George facing the Dragon, the two young men fight the thing almost to the death. When it quits, they push it; they badger or con mechanics to repair it.

The intimacy between the two men is beautifully evoked as well. The handsome Mexican actor Gael Garcia Bernal (he broke through in 2001's "Y Tu Mama Tambien," along with Diego Luna) plays Ernesto as a saint in training. He's all burning eyes and gentle nature, but you see him recording, calculating, theorizing. If you know Che's life a little, you can connect with foreshadowings of the future: Despite his asthma, he physically outperforms the heavier, stronger Alberto in all tests involving strength; that's an example of his buried, astonishing will. But he's a little bit of a goody-good, so the contrast with Alberto (Rodrigo de la Serna) is well done.

De la Serna, an Argentine, is a kind of proto-John Goodman, a heavy charmer, a con man on the make, with a merry, larcenous twinkle in his eye and a fondness for the girls that always gets him into trouble. He's also got a hair-trigger temper and is always exploding in frustration or wrath at his more repressed partner. But you feel a love between the men, even if one was to become an icon dead young in the jungle and the other a doctor with a long life ahead of him (the real Alberto is pictured at the end of the film).

Finally, Salles has a great feel for light and landscape. This is one of those films that finds emotional meaning in the earth: We see endless pampas, and raggedy mountains and sweltering jungles. We see ramshackle, un-quaint small cities far from the tourist's South America; we see endless, wide rivers and everywhere feel the fragility of the lives that people try to eke out from these zones.

I wish Salles had ended the film without the blather of leftist trumpet-blowing on a title card; he's speaking loudly when the film before has spoken softly. But the film itself, shorn of the noise in the last seconds, is a surprisingly effective re-creation of a Latin American Bing and Bob on the Road to History.

The Motorcycle Diaries (128 minutes, at Cineplex Odeon Dupont Circle and Landmark Bethesda Row) is rated R for a surprising streak of profanity.

Gael Garcia Bernal plays the young Che as a saint in training, all burning eyes and gentle nature. Rodrigo de la Serna, left, and Gael Garcia Bernal star in "The Motorcycle Diaries," about Che Guevara's eye-opening travels through South America.