While aerodynamics was the ‘priority’ for Quartararo and Rins, the Frenchman also tried out engine and chassis developments.
“There were some big changes, especially on the aero side," said Quartararo, who finished the test 12th fastest (0.769s).
"I think the direction we took was the right one. We made a step in this area."
But the other developments had been less fruitful.
“We tried new a chassis, but it was not so great, and the engine is really similar. Slightly better but just a little,” said Quartararo.
The former world champion had missed Sunday morning's Valencia GP warm-up due to illness but was able to complete 63 Tuesday laps.
"I have to keep going with the antibiotics for a few days, but today was much better."
Rins, riding his third different brand of MotoGP machine in just over a year, spent most of the day acclimatising to the M1 before also trying the new aero.
The former Suzuki and LCR Honda race winner was 19th quickest but within 1.3s of test leader Maverick Vinales.
“It was my first day with the Yamaha team, and I‘m so happy because it was a really good day,” said Rins, who rode for 54 laps on his return to an Inline engine layout.
“We tested many things: small things regarding set-up. We only worked on the aerodynamics. I‘m quite happy because I adapted quite well to the bike so early on.
“The last hours, from midday to the end of the session, we were trying fairings, and they made a step forward compared to the fairing I used in the morning, which was the race fairing.”
Team director Massimo Meregalli confirmed: “We mainly worked on three different items with Fabio today: aerodynamics - which was our priority, the first step of the 2024 engine, and a new chassis.
“Alex adapted so quickly to the bike that he too had the opportunity to test the new fairings.
“One day was maybe not enough to get everything set up perfectly because we had so many things to try, but all in all it‘s been a positive day. Both riders noticed an improvement, and this confirms our course of action has been the right one.
“We will send all the data to Yamaha Motor Company in Japan and Yamaha Motor Racing in Italy, where the Yamaha engineers will work tirelessly to prepare the next steps for the tests in Sepang.”
Due to the revised concessions rankings, Quartararo and Rins will now be able to take part in the Sepang Shakedown test as well as the Official test, next February.
"Hopefully at Sepang, we can be at our 100%," said Quartararo.