Jonas Folger will replace Alberto Moncayo at the Mapfre Aspar Moto3 team from the forthcoming Indianapolis round.
18-year-old German Folger, a former 125cc race winner, has finished in the points once (eleventh) from seven starts for the Iodaracing team, which is building and racing its own Moto3 bike.
Folger will race a Kalex-KTM alongside junior class veteran Hector Faubel. Faubel is twelfth in the championship.
"I am delighted to be signing for the Mapfre Aspar Team,” said Folger. “It is probably the most experienced team in the paddock and I know how professional they all are. I am highly motivated and will work as hard as necessary to make the most of this opportunity.
“My objective is to squeeze every bit of potential out of the Kalex, which is a very reliable bike in terms of the chassis and the KTM engine. It is a fast bike and it looks quite easy to ride so I am very much looking forward to riding it, meeting the team and getting down to work."
21-year-old Moncayo took a career best second place in the wet French Grand Prix, Aspar's only podium of the year, but has failed to score in the last three events. His future is unclear.
Aspar won the final 125cc class title with Nico Terol.