With Harley-Davidson losing interest, things got tougher.
In 1977 he finished third in the 250 cc championship and then faded from the racing scene to concentrate on the engineering company he and Francesco had built up in Modena.
He got his big chance the next season when he replaced Gianfranco Bonera, who had left to join the MV Agusta team, in the Harley-Davidson set-up.
Fighting off the fierce challenge of his own team-mate, Michel Rougerie, and a host of Yamahas, he won the 250 cc World championship and held it for a further two years.
At first he rode Mondials, but in the final year he and Francesco both rode two-stroke racers that they had designed and built in a small workshop at Modena.
His elder brother Francesco won the Italian 125 cc championship four times; Walter won the same title three years in succession, from 1966 to 1968.7, at Cedars-Sinai in Los Angeles, her rep confirms to PEOPLE exclusively.