Ivy started racing motorbikes at Brands Hatch, Kent, UK in 1959. His first race bike was a 50cc Itom. Entering his first TT race in 1962 on a Chisholm Itom, he later progressed to ride a variety of machinery on UK short circuits including Honda, Bultaco, Yamaha, Norton, Cotton, and Matchless machines. He joined the Tom Kirby racing team in May 1965.
Ivy's big break into Grand Prix motorcycle racing came towards the end of 1965, when he was selected as a stand-in and flown to Japan in October by Yamaha due to regular rider Mike Duff crashing in practice for the Japanese GP, suffering a broken thigh. Ivy finished fourth in the 125 cc race and third in the 250 cc class, the highest-placed of the Yamahas. In 1966, he won his first race as a regular rider for the works Yamaha team in the first race of the year, the Spanish Grand Prix at the Montjuic Park Circuit, Barcelona in Spain, and took three more wins—not enough, however, to beat Swiss rider Luigi Taveri, who beat Ivy to the title by six points. In 1967, Ivy dominated the 125 cc championship: he won eight out of twelve races to claim the World Championship by 16 points over Phil Read. On top of this, he won two 250 cc races in France and Belgium. In 1968, Ivy and teammate Phil Read controlled both the 125 and 250 cc championships. In the process Ivy also became the first 125cc rider to lap the famous Isle Of Man TT Mountain Course at over 100 mph. As the season progressed, Yamaha ordered them to win one title each, with Ivy scheduled to win the 250 cc championship and Read the 125 cc championship. After securing the 125 cc title, Read ignored Yamaha's orders to tie with Ivy on points. The tie break was decided on overall race times, and Read took the title. Ivy announced his retirement from motorcycle racing, stating he would race Formula Two cars during the next season.
Death
Despite showing some impressive results in Formula Two, in order to further fund his car racing, he was enticed back to motorcycling by an offer from Jawa in 1969 to race their 350 cc motorcycle. The season started promising, as he took two second places behind Giacomo Agostini. However, during practice for the fifth race, on the Sachsenring in East Germany, his motorcycle's engine seized due to the breaking up of the lower left hand connecting rod bearing cage. He was thrown from the bike, his helmet came off. He and the bike slid off the track where he impacted an unprotected fence post before bouncing back to the edge of the racing surface. His helmet was recovered from the opposite side of the track. Ivy died from injuries received in the impact with the fence post. Injuries were listed as a fractured skull, brain hemorrhage, fractured ribs and a large puncture to at least one of his lungs. He was brought back to Ditton, near Maidstone, Kent where a service took place at St. Peter's Church, followed by a private service and cremation at Medway Crematorium, in Blue Bell Hill Village, Kent.