'Butch and Sundance: The Early Days" is the first attractive Western to mosey across the screen in several years. Not a great or even rousing Western, but at least a pleasant, warmly evocative one, beautifully visualized and incidentally enjoyable for its settings, texture, droll tone and sometimes amusing interplay or characters.

It's surprising to see Richard Lester associated with a picture this relaxed and eccentrically preoccupied with period evocation. Directing his first Western Lester sustains a cheerful, serenely contemplative style, aided immeasurably by cinematographer Lazslo Kovacs and production designer Brian Eatwell. Ht eanecdotal structure may be too rambling and miscellaneous to inspire much excitement, but "Butch and Sundance" is never less than a pleasure to look at.

We're accustomed to sequels. "Butch and Sundance" attempts ot backtrack and account for the association of Butch Cassidy and the Sundance Kid before they became the notorious outlaws portrayed by Paul Newman and Robert Redford a decade ago. The youthful Butch and Sundance are played by Tom Berenger and William Katt, respectively.

Although they bear certain resemblances to Newman and Redford (Kratt, of course, looked like Redford's heir apparent three years ago in "Carrie"), the newcomers are distinctive and skillful enough to impose interesting images of their own.This movie isn't forceful or glamorous enough to bring them stardom, but Berenger and Katt work together deftly and their characters reveal shadings and tensions that never broke through the glittery, jocular surface of the original film.

Despite its diffuse elements, Allan Burns' screenplay has far more wit and feeling than the precious, cluttered text he supplied for "A Little Romance," which was directed, ironically, by George Roy Hill, the director of "Butch Cassidy and the Sundance Kid." Burns' dry, delayed-action sense of humor also contrasts radically with the emphatic tone of William Goldman's writing on "Butch Cassidy and the Sundance Kid," where every witticism seemed to be echoed by a hee-haw, heard or implied.

Perhaps Burns' restraint inspired Lester's uncharacteristically easygoing direction. Originally a slapstick streamliner, Lester settles into such a lulling rhythm that his timing of even the wildest escapades of Butch and Sundance feels a trifle poky.

Amiable Butch is introduced upon his release from prison in Wyoming. He encounters the laconic, sharpshooting Sundance when the latter shoots his way out of a card game he has tried to win at gunpoint. Impressed by his performance, Butch makes contact with Sundance, proposes a partnership and is eventually accorded one.

Burns creates a little suspense by having Sundance stalked by a relentless lawman (Peter Weller) and Butch by an alienated associate (Brian Denehy in a delightfully scroungy, threatening characterization). However, the story threads aren't tightly interwoven. While the eventual showdown with Dennehy produces a remarkable sequence, one experiences it as a superior rather than decisive episode, which it might have been in another sort of Western.

Under the circumstances nothing very decisive can happen. Burns' chronology of the young Butch and Sundance fades into the chronology of the original film about the outlaws in their maturity (sort of). Since the characters have chosen outlaw careers before we meet them, the filmmakers can only be suggestive about their formative experiences.

The screenplay takes a fascinating serious turn when Sundance is wounded, compelling Butch to take refuge at what turns out to be his home. It comes as a stunning, complicating surprise to perceive this boyish outlaw as a husband and family man as well. Moreover, it gives a melancholy undercurrent to the inevitable return of Butch and Sundance to criminal pursuits, this time with blood on their hands.

As embodied by Jill Eikenberry, Butch's wife, Mary, is not a woman you would choose to be separated from for long periods of time. As one of his sons, a little boy named Patrick Hamilton expresses such heartfelt confusion and unhappiness at the prospect of Butch suddenly leaving home again that the episode generates more sentimental wallop than anyone could have anticipated.

But the continuity isn't prepared to capitalize on those emotions. Butch and Sundance drift into a trainrobbing caper that is clever and entertaining, but essentially a complete change of pace. Soon afterward the movie draws to a halt more or less arbitrarily.

Shot on marvelous locations in Colorado and New Mexico, the production is further enhanced by a systematic insertion of amusing period details. Perhaps the most diverting are the homemade separator operated by a family dog walking a treadmill and a huge storefront advertisement for a "tonic" that promises truly appalling benefits.

"Butch and Sundance" isn't a complete recovery, but it stores some of the humor and affection that seemed permanently lost in misbegotten Westerns like "Comes a Horseman," "Goin' South" and "The Missouri Breaks," It makes Westerns look possible and desirable for a change. CAPTION: Picture, William Katt, left, and Tom Berenger in 'Butch and Sundance'