July 4, 1983

Clay Bernabeo is obsessed with racing. He races every Saturday and Sunday and at least three nights during the rest of the week. He was up at 8 this morning. He wolfed down breakfast and left his home in Forked River by 9. At 11:30, he arrived at the race track here. Already wearing his $90 red, white and blue nylon racing suit, he pulled on his $75 fiberglass helmet, his $20 goggles, his $30 specially soled shoes and then climbed onto his $850 bike. ''I love racing,'' said Clay, staring out at the track. ''Racing is cool.'' The wheels on the bike are only 20 inches high. But Clay fits comfortably. He is, after all, only 5 years old. Clay, his brother, sister and parents are caught up in one of the most popular children's sports activities since Little League baseball began. Officially it is called bicycle motocross. To children across the country, it is simply BMX.

Just before Christmas in 1977, a suitcase unloaded from an Alitalia flight from Sicily was discovered going round and round, unclaimed, on a Kennedy Airport luggage carrousel. The Customs agents who opened it found heroin, but no clue to the owner. Three months later, two passengers on another Alitalia flight from Sicily were seized with a still larger load of heroin. Federal agents, remembering the unclaimed suitcase, studied the list of passengers on the December flight and learned that a brother of one of the two men just arrested had traveled on it. Someone, the agents theorized, had developed a smuggling pattern, and they wondered how many times it had already been used successfully. Five-Year Effort In five years of working to delineate that pattern, more than 100 agents here and in Italy unearthed a complex conspiracy involving top organized-crime figures in both countries. Last month an Italian tribunal convicted more than 60 people in connection with the heroin ring, including such reputed organized-crime figures as Salvatore Gallina and four members of the Gambino family.

One of the biggest gambles in the history of particle physics paid off yesterday when Fermi National Laboratory in Batavia, Ill., announced that it had successfully pushed protons to nearly the speed of light with a new atom smasher of revolutionary design. The success ends a decade of worry and work on the project and marks the inauguration of the world's most powerful machine for probing the heart of the atom. The whirling protons in the new accelerator reached energies of 512 billion electron volts, the highest ever attained. Though that is just above the 500 billion electron volts reached by the laboratory's older accelerator, the new energies are enough, the machine's designers say, to allay their anxieties about mastering the new machine's advanced technology. Stretching four miles in a circular tunnel beneath the Illinois prairie, the accelerator is the first to guide speeding particles with powerful superconducting magnets. These make feasible the construction of cheaper, smaller and more energetic atom smashers.

The Reagan Administration is resisting growing pressure to allow hundreds of thousands of Salvadoran refugees, who have entered this country illegally, to remain. From Spanish Harlem in New York to crowded Central American neighborhoods in Los Angeles, Federal immigration officials estimate, more than 500,000 Salvadorans are living illegally in the United States. Tens of thousands are seeking political asylum here, clogging the nation's already jammed immigration courts, but few are being granted it. The Administration asserts that granting them asylum or even temporary legal status, as members of Congress and volunteer organizations have urged, would invite millions of impoverished Central Americans to seek a better life here. There were about 4.5 million people recorded in El Salvador's 1980 census.

Since December, groups of up to 1,000 Communist insurgents and their supporters have been marching out of the jungles waving red flags, to be greeted by speeches, television cameras, meals and the Thai Army's senior generals. The defections, most of which have taken place in the northeast, have been spurred by Government offers of amnesty and aid. But the rebels' emergence from the wilds of Thailand is also graphic evidence that an insurgency that has severely harassed, though not threatened, the rulers of the country for nearly 20 years is breaking up. While rurally based revolutionary movements have been thriving in other parts of the world, the outlawed Communist Party of Thailand has been losing guerrilla supporters, weapons and prestige. Abandoned by Peking The movement here, linked for many years with China but then abandoned by Peking, appeared to be growing until recently. China apparently attaches greater importance now to its relations with the Thai Government of Gen. Prem Tinsulanonda.