During 1984 Garelli began work on a new racer for the 250cc class. Designed by Jan Thiel, it first ran towards the end of the year and was track tested at Monza in November by new signing, Maurizio Vitali. The new engine was a water-cooled v-twin with disc valve induction, which went into Garelli's trademark aluminium monocoque frame, an aperture being cut in the left side to enable access to the rear cylinder's spark plug. White Power suspension was used at both ends, the front fork being equipped with the now familiar mechanical anti-dive. With 72bhp on tap at 12,000 rpm, Garelli's new quarter-litre racer had a top speed of around 250km/h (155mph).

The 250 Garelli made its Grand Prix debut in March 1985 at South Africa's Kyalami circuit,where its lack of competitiveness must have come as a bitter blow for a team that had grown accustomed to unalloyed success in the 125 class. In the race, Vitali finished 13th while star rider Angel Nieto failed to qualify. Indeed, so disillusioned was Nieto that he suggested the monocoque be ditched in favour of a tubular frame sourced from the Spanish manufacturer, Kobas. Nieto failed to get his way and left Garelli at the end of a disastrous season, Vitali's 6th place in Spain being the team's only finish in the points. As it happened, Nieto would be proved correct when a tubular frame tried at Misano at the year's end demonstrated that the monocoque was simply too low. Nevertheless, Fausto Gresini's first 125cc World Championship provided