DALLAS (AP) _ The founder of the 7-Eleven stores, the world's largest convenience store chain, said Thursday it is selling control to a Japanese company because of crushing debts from a junk bond-financed buyout.

The announcement by Southland Corp., which owns 7,000 7-Elevens in the United States, is one of the most dramatic examples yet of the problems facing U.S. companies that participated in the junk-bond craze of the 1980s.

Southland said it agreed to sell 75 percent of its common stock for $400 million to Ito-Yokado Co. Ltd., Japan's second-largest supermarket operator, and longtime Southland affiliate 7-Eleven Japan, which Ito-Yokado controls.

Besides the company-owned 7-Elevens, the deal includes Southland's six food processing centers and five distribution centers.

In addition to the 7,000 Southland-owned stores, independent licensees operate nearly 6,000 7-Elevens in the United States and 21 other countries, including nearly 4,000 in Japan. Their merchandise features milk and frozen foods, newspapers, hot coffee, video rentals and slushed ice drinks. The chain began in 1927 as a Dallas ice house.

Southland, which sought the Japanese buyer, said the deal hinges on its ability to get 32 bank creditors to restructure terms of the company's outstanding preferred stock and $1.8 billion in debt. Much of the debt is in high-interest junk bonds used to finance the $4.9 billion leveraged buyout by Southland's founding Thompson family in 1987.

Almost immediately after the buyout, the company had problems meeting huge debt payments. It attempted to raise cash partly by selling such assets as a half-interest in Citgo Petroleum Corp., a major refiner.

''We believe this transaction is necessary to preserve the business we've built,'' said Southland Chairman John P. Thompson, son of founder Joe C. Thompson.

Thompson's family will retain a 15 percent stake in the company and positions on the board of directors.

He said the $400 million infusion by Ito-Yokado would enable Southland to make needed capital improvements and finance advertising and marketing efforts in the competitive convenience store business.

''There will be no layoffs and no store closings,'' Southland spokesman Harris Diamond said.

Other companies acquired with high-interest junk bond debt have suffered similar problems.

Campeau Corp., for example, earlier this year put its heavily leveraged Federated and Allied retail store empire under Chapter 11 bankruptcy court protection after they defaulted on credit agreements. Revco D.S. Inc., the drug store chain acquired in a $1.25 billion leveraged buyout in 1986, went Chapter 11 in 1988.

Masatoshi Ito, the chairman of 7-Eleven Japan and president of Ito-Yokado, said the deal is the beginning of a worldwide partnership.

''As the world's largest convenience store chain, we will maintain and build upon our mutually strong market positions by combining the operating skills and strategic thinking of the American and Japanese companies,'' Ito said.