Dick Motta, former coach of the Washington Bullets, will be named coach of the expansion Dallas Mavericks at a press conference in Dallas this morning.

Motta, who resigned after four years as Bullet coach, will be the new NBA club's first coach. It is expected that the Mavericks also will name Bob Weiss, a former Bullet player, currently a San Diego assistant, as Motta's assistant.

Motta, 48, has been a head coach in the NBA for 12 seasons, eight with the Chicago Bulls and four with the Bullets. He has the third-best winning percentage in league history and his 551 victories are third highest. In 1978, he led the Bullets to their only NBA title. In 1979, Washington had the league's best record and again made the NBA final, but lost to the Seattle SuperSonics.

Last season, the team was hampered by injuries and dissension and limped into the playoffs with a 39-43 record, bowing out meekly in two games to the Philadelphia 76ers in the first round.

Motta and the Bullets reached a "mutual agreement" on his resignation in May, although he has remained on the payroll as a special consultant.

Motta reportedly will sign a three-year contract worth $150,000 annually. "We're grateful to have what we believe to be one of the strongest coaching tandems (with Weiss) in the league," said Norm Sonju, Dallas general manager.

Sonju and team owner Don Carter flew to Idaho last weekend to meet with Motta and apparently that meeting resulted in the agreement.

Boy Ferry, Bullet general manager, said yesterday Washington will receive no compensation for Motta in cash or draft choices. "We told Dick that he had permission to talk to anyone he wanted to and there would be no compensation involved," Ferry said. "I think this is the best move Dallas has made so far."

Motta was in Dallas yesterday and could not be reached for comment. He will take about 30 players with him to training camp in September, 22 acquired in the expansion draft, plus the team's college draft picks.

The Mavericks' No. 1 choice is Kiki Vandeweghe, a UCLA forward. Among the expansion players is Jim Cleamons, who played last season with the Bullets and has been described as a Motta-type player -- not very talented, but a good thinker.