A 14-year-old from Baltimore set seven national records today on the first day of weightlifting competition in the Amateur Athletic Union's Junior Olympics.

Joseph Beauchemin set three snatch records and two clean and jerk marks, and went over the national combined total weight record twice in the 12- to 13-year-old division.

Beauchemin competes in the junior division because he was 13 at the start of the 1983 season.

He finished the day with a snatch lift of 231 pounds and a clean and jerk lift of 270 pounds.

Beauchemin missed out on a national record in Maryland's weight-lifting meet because no national judges were on hand.

"That was my plan (to get the record) when I broke it unofficially in the state meet," he said.

Beauchemin got up to 231 pounds with a snatch lift--a straight lift from the floor to overhead in one motion--twice before in practice.

He also has gone as high as 281 in practice in the clean and jerk--one motion from floor to chest and then from chest to overhead.

Nearly 2,000 athletes began track and field competition today, the fourth day of the games. Also getting under way was competition in swimming, boys and girls basketball and water polo.