Riboco (7-2), with Lester Piggott up, earned owner Charles Engelhard of Far Hills, N.J. first-place money of $119,546 when he defeated Queen Elizabeth's Hopeful Venture by 1� lengths in the St. Leger stakes—the last classic race of the English season—in Doncaster, England.
Hobeau Farm's MAC'S SPARKLER ($18.80), with Bill Boland aboard, finished a neck in front of Triple Brook to take the $81,900 Beldame for fillies and mares, at Aqueduct, while Mrs. Ethel D. Jacobs' Straight Deal, the favorite, wound up fourth, 2� lengths behind Gamely.
Estreno II ($250.60), with Carlos Marquez aboard, scored a stunning upset in the $125,800 Michigan Mile and One-Eighth when he beat Handsome Boy by three-quarters of a length. Handsome Boy was disqualified for interference and placed fourth, behind Tenzing II and Carpenter's Rule.
Diplomat way ($3.40), with Milo Valenzuela up, set a track record of 1:34[3/5] in winning the first division of the $23,275 Chicago Handicap at Hawthorne raceway, but in the second division, also worth $23,275, Walter Blum rode CANAL ($7.40) to a new mark of 1:34[1/5] for the mile race on turf.
MODERN PENTATHLON—HUNGARY gained the world championship in J�nk�ping, Sweden for the third consecutive time with an accumulation of 14,237 points, 590 ahead of Sweden. The U.S.S.R. came in third, while the U.S. finished way back in 15th place.
MOTOR SPORTS—Grand Prix Formula I leader DENIS HULME of New Zealand, averaging 109.13 mph in his "Flower Power" Chevrolet, gained his second consecutive victory in the $500,000 Canadian-American Challenge Cup series by taking the SCAA Bridgehampton ( N.Y.) Grand Prix by 48 seconds over his teammate Bruce McLaren.
Jack Brabham of Australia drove his Brabham-Repco at an average speed of 106.37 mph to beat Jackie Stewart of Scotland by five seconds in the Gold Cup Formula I and II race in Oulton Park, England.
POLO—With Benny Gutierrez scoring six goals, the MILWAUKEE POLO CLUB defeated Keswick of Virginia 11-7 in the finals of the National 20 Goal tournament in Milwaukee.
RODEO—LARRY MAHAN, a 23-year-old cowboy from Brooks, Ore. who was last year's top money winner on the professional rodeo circuit with $40,458, drew closer to repeating as the All-Around Champion when he gained the All-Around title and $1,985 at the Pendleton (Ore.) Roundup. Mahan's winnings this year now total $37,604.
MILEPOSTS—NAMED: Head track-and-field coach of the U.S. team for the 1968 Olympic Games, PAYTON JORDAN, 50, coach at Stanford University the last 12 seasons.