Yamaha has brought a halt to its Sepang MotoGP Test as a result of concerns with its V4 engine.

The Japanese manufacturer introduced its V4 MotoGP engine during the 2025 season when Augusto Fernandez rode with it at during tests and in wildcard appearances at Misano, Sepang, and Valencia. The race riders were also able to ride the V4 bike in private tests towards the end of last season, as well as in the post-season test in Valencia.

Yamaha confirmed during the Valencia Grand Prix weekend that it would replace its inline-four engine with the V4 for the final year of the 1,000cc MotoGP regulations in 2026.

No reliability issues were reported with the engine during last year, although there were continuous reports that the engine had not been run at full power.

During the Sepang test, however, Yamaha has discovered technical issue with the engine significant enough for it to pause its test on the second day.

“The team is still investigating the technical issue from yesterday,” Yamaha told Crash.net. 

“As a precaution, and until all checks are completed, the test is temporarily on hold.

"We expect to resume as soon as possible.”

Crash.net reports that the technical issue on Monday mentioned by Yamaha was related to the engine.

Additionally, The Race reports that it was told by Yamaha’s factory MotoGP team director Massimo Meregalli that the halt to its testing was “for a pure safety matter” to give engineers time to understand the issue.

The issue was found on the bike of Fabio Quartararo, who crashed at turn five late on Tuesday, but Meregalli said the issue was not “related” to the Frenchman’s crash that left him with a broken finger and thus out of the remainder of the test even before Yamaha decided to, at least temporarily, stop its Sepang test.

With Quartararo ruled out through injury, Yamaha still had five riders lined up to test today: test riders Augusto Fernandez and Andrea Dovizioso; and race riders Toprak Razgatlioglu, Alex Rins, and Jack Miller.