Mercurial Italian sprinter Pietro Mennea, reluctant to come to the Olympic Games because of the United States-led boycott, dramatically won the gold medal in the 200 meters today, overtaking 100-meter champion Allan Wells in the final strides after a terrible start.

Mennea's victory in 20.19 seconds -- well off his world record of 19.72 set a high altitude last year -- came after much soul-searching and a settling phone call from older brother Vicenzo, who reassured him from Italy that he was doing the right thing despite his political misgivings.

The brilliant, but erratic Mennea's golden moment, after 12 years of training that he says he would not go through again for $5 million, was the human interest highlight of the day at the Controversial Moscow Games.

The greatest athletic achievement belonged to East German long jumper Lutz Dombrowski, who won the gold medal with a leap of 28 feet 1/4 inch. It was only the second jump in history or more than 28 feet.

The world record in the long jump, of course, is American Bob Beamon's 29 feet 2 1/2 inches -- one of the most astonishing feats in sports history, achieved in the 7,500-foot altitude of Mexico City during the 1968 Olympics. a

Many track and field aficionade consider Beamon's futuristic record unapproachable, at least in this century. When he hurtled through the rarefied air of the Mexican capital, pumping his legs like a man walking through space, the outer limits of human capability may well have soared with him.

But Dombrowski's leap today, on the fifth of a remarkable series of jumps into the sandy pit at 103,000-seat Lenin Central Stadium, was immediately hailed as "the sea level world record."

It exceeded the second best jump ever, American Larry Myricks' 27-11 1/2 at the World Cup in Montreal last August. Dombrowski was second that overcast afternoon at 27-1 3/4.

Myricks is absent because of the boycott by the U.S. and approximately 50 other countries, and that diminished the long jump competition. Dombrowski's accomplishment gave his medal credibility, however, and unleased a wild scene of East German dancing, singing and flag-waving in the stands.

Dombrowski, 21, has appealingly boyish looks. He is fair-haired, with a few wisps of blond stubble on his chin. He is extemely muscular at 6-1 1/2 and 191 pounds, but looks smaller when he competes -- perhaps because of his boyish striped knee socks. He works as a millwright at a steel plant in his native Karl-Marx-stadt.

He almost didn't make the Olympic team because a pulled muscle in his right leg sideline him the first half of the year. The East German Athletic Federation arranged a special competition July 5 to enable him to demonstrate his fitness, and he jumped 27-8 3/4, equaling the third best mark of all time.

Dombrowski vertified that form today with a remarkable series. All five of his jumps exceeded 26-9. He passed on his third jump, feeling fatigued on the warm and sunny afternoon and preferring to marshal his strength.

Fellow East German Frank Paschek took the silver medal with 26-11 1/4, and Valery Podluzhnyi of the Soviet Union was third at 26-10. Six jumpers cleared 26-3, the first time this has been accomplished in the Olympics.

Dombrowski took up jumping 12 years ago and uses a simple and old-fashioned technique. He was pleased to exceed 28 feet in Moscow, which is a few hundred feet above sea level. But he has no designs on Beamon's world record, at an elevation.

Asked if he thought that would stand as an "eternal record," he said, "No, all records are broken eventually, but I don't think I will do it. I am not in that class."

Three Olympic track records fell today when Vera Komisova of the Soviet Union won the women's 100-meter hurdles in 12.54 seconds, Marita Koch of East Germany took the women's 400-meter gold medal in 48.88, and Soviet Natalya Bochina lowered the 200-meter record with a clocking of 22.25 seconds in a preliminary hear.

Viktor Rasschupkin of the Soviet Union won the gold medal in the discus with 217 feet 10 inches -- well below the 1976 Olympic record of 221-5 set by Mac Wilkins, who is absent because of the boycott. Rasschupkin is a ringer for comeian John Belushi.

World record holder Wolfgang Schmidt (233-5 1/2) of East Germany, who was expected to duel Wilkins for the gold until politics intervened, shocking finished fourth. The best of his four throws was 215-4 -- he fouled on his first and last attempts -- and he finished behind silver medalist Imrich Bugar of Czechoslovakia (217k-9) and Luis Delis of Cuba (217-7), who took the bronze.

Plenty of other interesting things happened at Lenin Stadium.

Alberto Juantorena, Cuba's 29-year-old "El Caballo" (The Horse), the gold medalist at 400 and 800 meters four years ago, kept his comeback bid barely alive in the 400. Juantoreno, who had Achilles tendon surgery in March, finished third in his semifinal heat in 45.95, and qualified for the final by two-hundredths of a second.

Juantorena appeared to hit the finish simultaneously with Joseph Coombers of Trinidad and Viktor Barakov of the Soviet Union, but was timed .01 faster than Coombes and .02 faster than Burakov, who was eliminated.

Lasse Viren of Finland, fifth on Sunday in defense of the 10,000-meter gold medals he won in 1972 and 1976, dropped out of the 5,000 meters today and decided to run in the marathon Friday instead.

Viren also won the 5,000 meters in 1972 and 1976, but did not show up for the heat in which he was scheduled to run against Ethiopian Miruts Yifter, who wore him out in a grand race and won the 10,000-meter gold. Yifter, who says he is 36 years old but looks 50, looked fresh as ever in winning that 5,000-meter heat today. the 5,000 final also will be held Friday.

For sheer human emotion though, no event today surpassed the 200 meter dash in which Mennea outkicked Wells, the fleet Scotsman attempting to become the eight man in Olympic history to win both the 100 and 200-meter sprints.

Mennea, 28, graduated with highest honors in political science this year from the University of Bari, but came to Moscow a troubled man.

He did not feel in good shape physically. Even though he had not lost a 200-meter race in 1980, he was concerned about the leg injury in March that had put his training schedule into a shambles.

He was even more concerned about his mental condition. "Physically I can do it, but in the head, I'm not sure," he said when he came to Moscow. Even then he was not certain that he would run, and kept his adoring countrymen on tenterhooks as to his intentions.

He was appalled by the Soviet military intervention in Afghanistan, and though he should support the boycott. Even after the Italian Olympic Committee voted to participate in Moscow, using the Olympic flag and anthem because the Italian government forbade the use of the Italian national flag and anthem in connection with the Games, he hesitated. He was sensitive to advice that he stay away from the Games.

But he did not want to see the Olympics destroyed. "I had a lot of doubts, but I wanted to see the Games continue. I thought my presence here would help," he said.

Still, he was uncomfortable. The fact that he lost in the semifinals of the 100 meters didn't help -- though there are some who contend he ran that race only to get the look and feel of the track before the 200, which is his event. "You must understand, I have a mental block about the 100, he told an Italian journalist.

His discomfiture increased when he was drawn to run today on the outside, in lane No. 8. A swirling breeze made it even more difficult. Beside him in lane 7 was Wells -- the only European to beat him over 200 meters in seven years, having done so last August in the Europa Cup before 70,000 startled Italians in Turin.

"The pressure of being the favorite with no Americans here, and the bitterness of the boycott and running in this crippled event, cracked my nerves; I was sick in here," Mannea said, pointing to his head.

The call from his brother back home in Barletta helped. Barletta is a little town near Bari on the Adriatic coast in the "heel" of the Italian "boot," famous in medieval history as the site of a pitched battle between 13 French and 13 Italian knights.

Despite the presence in the race of 1976 gold medalist Don Quarrie of Jamaica and swift Silvio Leonard of Cuba, Menna knew that Wells was the one man he would have to beat.

"He was the one danger, nobody else; I had picked Wells to win the 100, and he was very strong," Menna said 20 minutes before the race. "But I will show him my back in the 200."

Menna started horribly. Wells, who only began using starting blocks this summer after 12 years of sprinting without them -- they are now required in the Olympics as a means of activating a sophisticated timing device -- got off to an an explosive start.

Wells, also 28, made up the two-yard staggered start in no time and was past Mennea, seemingly in position to dash home to his second gold medal. But anyone who ever doubted Mennea's heart should have seen him make up ground today, and fly by Wells in the home straight.

Mennea's 20.19 was two-hundredths of a second better than Well's silver medal time. Quarrie was third in 20.29, failing in his effort to become the first repeated winner of the 200, and Leonard was fourth in 20.30.

As the swarthy Mennea crossed the line, he raised his arms triumphantly, did a little dance, then took a victory lap, even though that is not supposed to be permitted.

Trotting around the brick-colored, 400-meter oval, he stopped frequently in front of sections where Italians were waving red, white and green national flags, jumping up and down jubilantly, and chanting, "Pi-e-tro Pi-e-tro." He clapped his hands, too, applauding himself, and finished his long, slow jog with the index finger on his right hand held aloft, indicating "No. 1." Then he was swallowed up by a horde of Italian reporters and cameramen.

"At the beginning of the race, I lost my tempo," Mennea said later, "when Wells went by me, I wanted to stay with him -- but I knew from the 100-meter semifinal that he's two meters faster than me at 100 meters, so I must try to catch him gradually."

Catch him he did, and then spurted by. "I quieted all those who said I was finished," he said. "You can't be finished when you close a gap of three meters on the Olympic 100-meter champion coming down the stretch."

Wells was more astounded then anyone, "A wee bet surprised," he allowed in his thick Scottish burr, "that he passed me in the stretch. But he ran a super race. I can't be too disappointed with a gold and a silver."

How could Mennea finsih so strongly? "This is a mystery you cannot explain," said his coach, Carlo Vittore, who also had the definitive word on the way his man came from behind in the race: "You can also win in this way but it is mascochism."

Mennea, who teaches physical education, had set the world record of 19.72 last year at the World University Games in Mexico City, bettering the 19.83 mark of Tommie Smith -- still the Olympic standard -- achieved in the same high altitude in 1968.

Mennea had geared his training to peak at Mexico City in 1979, and at Moscow this year. But he feared that his injury and then anxieties over the boycott had ruined the carefully mapped plan.

When it counted most, though, he came through. "This is a great psychological victory, more than physical," he said. "It had to do with what's inside. Coming down that final stretch, I wanted to win. I wanted it very badly.

"There is only one Olympics. This was my last chance. After this, I can retire. It dosen't matter if I never win antoher race."

Politically, he still has mixed feelings. He was asked after his triumph of a lifetime how he felt when the Olympic flag was raised, and the Olympic hymn was played by the band, instead of his national flag and anthem -- a fact cleverly concealed by Soviet television, which showed Italians waving flags and singing their national anthem in the stands.

The sensitive, thoughtful Mennea gave a long, involved answer in Italian -- the kernal of which, according to Italian journalists, was that he regrets "that these Games are being used as a political instrument."

The offical Soviet translation into English was short, and not to the point. "I am very glad that I came," the host's version of Mennea's comments said, "because I think these are the best-ever Olympic games."