The Los Angeles Dodgers came alive behind rookie pitching ace Fernando Valenzuela to beat the New York Yankees 5-4 last night before an appreciative hometown crowd, cutting the Yankees' World Series lead to two games to one.

The expected pitching duel between Valenzuela, "the Mexican taco," and Yankee flame-thrower Dave Righetti did not develop, as both young pitchers were ragged and wild in the early innings. Dodger third baseman Ron Cey pulled a Righetti fastball deep into the left field bleachers in the first inning for a three-run homer, and Bob Watson, who has been hitting the cover off the ball all series, responded for the Yankees with a solo shot off a hang screwball by Valenzuela in the second.

Valenzuela came within inches of being taken downtown again in that inning, when Yankee catcher Rick Cerone hit a double that rebounded off the pipe railing on top of the left-field fence. Cerone got his homer in the third when he pulled a two-run blast to put the Yankees ahead, 4-3, but the Dodgers went ahead for keeps, 5-4, in the fifth, the winning run coming when Ron Cey scored on a double play gound-out off reliever Rudy May.

It was all Valenzuela from there on in, as the rotund left-hander set the Yankees down with growing ease the last four innings.

Valenzuela fanned Lou Piniella to end the game with a flourish as the crowd of more than 56,000--the most in Dodger Stadium history--exploded in tribute to their chubby hero.

The Yankees played again without the services of slugger Reggie Jackson, who is resting a hamstring strain. Third baseman Graig Nettles was also out of the lineup, but both are expected to be back on the field when the series resumes today at 4:30 p.m., Pacific Standard Time.

Jackson had told reporters that he wasn't losing sleep over being out of action since he'd been in the World Series so many times before.