Elizabeth Taylor and Malcolm Forbes denied rumors they were engaged to be married Sunday at the publishing mogul's estate in Bedminster, N.J., before they tooled off together on Liz's new, purple, 1988 Harley-Davidson 883--a gift from Forbes that day. The self-described "best friends" were followed by 50 members of the Capitalist Tools, Forbes' motorcycle club, as they headed for a day of races at a nearby track. The multimillionaire paid $4,500 for the modified chopper and another $500 for the custom paint job--chosen to match the packaging color of Taylor's new perfume. In return, Taylor gave Forbes a silver, helmeted skull ring with ruby eyes--similar to one Forbes gave her. The biker chums wore matching fringed red-leather jackets bearing the Capitalist Tools logo.