Ito began competitive racing in the All-Japan 500cc Championship on a Honda NSR500 from 1988, consistently finishing inside the top seven and claiming the Japanese 500cc title in 1990. During this period he also made his first appearances at the Suzuka 8 Hours endurance race, posting seventh-place finishes in 1988 (with Masumitsu Taguchi) and 1991 (with Daryl Beattie). He made occasional wildcard appearances in the 500cc World Championship from 1989 to 1992, finishing as high as fourth at the Suzuka round in 1992.
Honda rewarded Ito's domestic form with a full-time 500cc World Championship seat in 1993 alongside Mick Doohan and Daryl Beattie. Often assigned development components — including a fuel-injection system widely speculated to have appeared on his machine before any other — Ito scored four top-five finishes in his debut full season. His best result that year was pole position followed by third place at Hockenheim, and he finished seventh in the championship. He also became the first Grand Prix rider to exceed 200 mph (321.86 km/h).
In 1994 Ito scored points in eleven of fourteen races, nine of which were top-five finishes. His finest result came at Brno where he qualified seventh and finished second, just three seconds behind Doohan. He again finished seventh in the championship.
The 1995 season promised a breakthrough victory at Ito's home race in Suzuka. Leading comfortably in heavy rain with seven laps remaining, he was caught out by the wet conditions and crashed. He still managed two podium visits that year and achieved a career-best fifth place in the championship standings.
In 1996 Ito was tasked with developing Honda's new V-twin NSR500V, a machine underpowered compared to the V4 rivals. Despite scoring points in twelve of fifteen races, he could only manage sixth in the championship, and his best result was sixth at Catalunya. This was his final full season in the World Championship.
The Suzuka 8 Hours was the arena in which Ito arguably reached his greatest heights. He qualified on pole position five times at the event, equalling Wayne Gardner's record, and won the race four times:
1997 with Tohru Ukawa
1998 with Tohru Ukawa (from pole position)
2006 with Takeshi Tsujimura
2011 (having come out of retirement)
Alongside these victories he secured numerous further podiums and pole positions across his endurance racing career.
Returning to full-time domestic competition after his 500cc World Championship stint, Ito became a dominant force in the Japanese Superbike Championship on a Honda RC45. He won the title in 1998 and later added further championships in 2005 and 2006 on a Honda CBR1000RR, making him a three-time Japanese Superbike champion.
In 2000 Ito was recruited by Kanemoto Racing to conduct Bridgestone tyre development on Honda NSR500 machinery, alongside Nobuatsu Aoki. His development role led Honda to give him a Honda RC211V for the inaugural MotoGP race at Suzuka in 2002, where he qualified third — just 0.2 seconds behind pole-sitter Valentino Rossi — and finished fourth.
In 2005 Ducati brought Ito into a newly created Ducati-Bridgestone Tyre Test Team for MotoGP development. When works Ducati rider Loris Capirossi was injured, Ito took his seat at the Turkish Grand Prix, becoming the first Japanese rider to pilot a factory Ducati in a Grand Prix. He was given a race-through penalty for a jump-start violation, failed to serve it, and was black-flagged from the results. He then suffered a fractured thighbone during pre-season 2007 testing at Motegi.
At the 2011 Japanese Grand Prix at Motegi, Ito came out of retirement to ride as a wildcard alongside Kousuke Akiyoshi as a gesture of support for regions affected by the Tohoku earthquake and tsunami. He was 44 years old at the time and had won the Suzuka 8 Hours earlier that year to cap a remarkable return.
Shinichi Ito's career exemplified the role of the elite development rider — a racer who combines race craft at the highest level with the technical feedback skills to shape machinery for others. His five Suzuka 8 Hours pole positions, four victories, three Japanese Superbike titles, and long partnership with Honda in both domestic and international tyre development programmes earned him enduring respect within Japanese and world motorcycle racing.