Tech3 rider Johann Zarco will use the 2016 Yamaha chassis again at the next MotoGP test, having swapped back to it for the final day of this week's Sepang running.
As Yamaha's satellite team, Tech3 traditionally runs the previous season's chassis specification.
But last year Zarco was often able to outperform factory Yamaha riders Valentino Rossi and Maverick Vinales on their troubled 2017 M1 design with his '16 version.
Zarco was eighth and sixth using the 2017 bike for the first two days of the opening '18 pre-season test at Sepang this week, then reverted to the '16 chassis for Tuesday - when he was only ninth but happier.
"In the morning it was the perfect condition to be really fast and 1m59.5s is quite good but not good enough," he said.
"At least I could have the grip I was missing the day before.
"For what I feel at the moment, it is a better option for me because it makes my work easier."
Zarco will stick with the 2016 chassis for the next test at Buriram in February, and wants to try to emulate the riding style Jorge Lorenzo used when he was at Yamaha.
"I still have things to learn so for the next test I will keep working on the bike that I was using last year," he said.
"[I want to] find a way to ride it as Lorenzo was riding it two years ago because I think doing what he is doing will help me to be faster."