"Breaking Away" as a TV program retains most of the funiculi and much of the funicula of the Oscar-winning motion picture. It even retains some of the Rossini. But it also, at times, suggests second-hand brio , the summer-stock version of a movie millions took to their hearts last year.

In the premiere of ABC's one-hour comedy-drama at 8 tonight on Channel 7, Shaun Cassidy proves a very satisfactory replacement for Dennis Christopher of the original film; he is likable, bright, and believably eccentric. But he often has to go through emotions already gone through in the film, and so it's hard for him to be very fresh in the role of the callow youth who clings to a romantic view of life, no matter what.

Steve Tesich, who wrote the screenplay for the movie, also wrote the premiere episode. While it does more than just condense the movie, about youth and yearning in a Midwestern town, it doesn't quite amount to a free-standing work. It's too dependent on memories of the movie, though fortunately possessed of the same engaging spirit.

In addition to the participation of Tesich, Peter Yates, the director of the original film, is executive producer for the series. Its cast includes two holdovers from the movie: Barbara Barrie as Mom, and Jackie Earle Haley as Moocher, who goes off like Mount St. Helens when he hears an epithet like "Shorty."

Replacing the irreplaceable Paul Dooley in the role of Dad, a long-suffering used-car salesman, is Vincent Gardenia, who has done the annoyed papa routine so often it has become rather uninteresting second-nature to him. Thom Bray as Cyril doesn't fully capture the rumpled poignance of the wisecracking kid he plays, but Tom Wiggin does all right by Mike, one of those guys who think they can get by on their looks.

The program benefits from an unusual hip-folksiness and, unusual for television, a sense of Americana and of small-town locales, although it was actually filmed in Athens, Ga., intead of Bloomington, Ind., where the story takes place.

Again, the struggle of the poor young townies to maintain their self-respect in the face of snubs and condescension from the rich, transient college kids, makes watchable, flavorful conflict. But there is the unpleasant indication that the show may degenerate into nothing more than a series of fights -- the BMOC's vs. the "Cutters" (descendants of stonecutters) week after week. This doesn't sound like much fun.

The urge to provide action on a simplistic level may take precedence over even token attempts at characterization and deep human comedy. Those who saw the movie may find it a real drag that the hero is still running around trying to be an Italian; by now he would have moved on to some other grand obsession as kids of this ago do.

These misgivings are brought up only because there's every opportunity for this series to depart from the usual deadly rituals of prime-time TV. Millimeter for millimeter, there's still more humor, charm and dimension to this filmed hour than to any other family series on the air. Tupperware parties like "Eight Is Enough" are put completely to shame; "Breaking Away" at least has the distinction of being the champion in a class by itself.