The Repsol Honda team has completed a two-day private test in Brno where riders Marc Marquez and Dani Pedrosa tested a new chassis.
The RC213V has shown a deficit to rival bikes under acceleration this season, forcing Honda riders to take risks trying to make up time under brakes.
According to Spanish sports daily AS, the factory Honda squad hopes that the developments will also improve the bike's stability under brakes and in cornering.
Pramac Ducati was also testing on Tuesday (local time) in Misano, with both Danilo Petrucci and Scott Redding on track.
The Red Bull KTM team has also been in action during MotoGP's winter break, holding a two-day private test at Aragon just over a week ago.
KTM's regular riders Bradley Smith and Pol Espargaro were joined by test rider Mika Kallio and Moto2 rider Miguel Oliveira, who rode a premier class bike for the first time.
The MotoGP World Championship resumes in Brno for the Czech Grand Prix on August 4-6.