Maverick Vinales says Franco Morbidelli "deserves" to have machine parity with the other factory Yamaha riders and thinks it would be "fantastic" to have four current-spec M1s on the grid.
Morbidelli is riding what Yamaha dubs its 'A-spec' bike in Petronas SRT colours, which is effectively a 2019 M1, while team-mate Fabio Quartararo is on full factory current-spec machinery.
The Italian was due to run the same factory bike as Quartararo for 2020, but Yamaha reversed this decision at the start of the year.
This set-up at Yamaha is set to continue next year, which will make the Japanese marque the only manufacturer with a satellite operation to not have four 2021 bikes on the grid next season after Honda confirmed a machinery upgrade for LCR's Takaaki Nakagami.
When asked if this would be a disadvantage for Yamaha, Vinales said: "Sometimes it's difficult to understand, because in a few tracks Franco was better than us and he's with the old spec bike.
"So, I prefer if everyone has the same spec bike so everyone has the same possibilities, especially when someone goes faster you understand why.
"Also, Franco is doing well, he deserves the same bike we have in our time.
"So, to be four factory riders in Yamaha would be fantastic.
"You can improve more because every rider can test something and this is very good."
San Marino Grand Prix winner Morbidelli believes it will be an "advantage" for Yamaha to have an old bike to compare data with its current machine.
"Well, actually I think it's more of an advantage for Yamaha because they can compare the data and they can see where the old bike is better and where the new bike is lacking, and the other way around as well," the Italian said.
"So, for Yamaha it's better.
"For me, not that much because they can work in order to improve what's missing on the new bike, I don't know if I can improve what is missing on the old bike.
"That's the whole situation, but I think for Yamaha to have four strong bikes and four strong riders, three new ones and one old one that is going fast as well, is just one more interesting package and some more interesting data.
"For them, I think it's better. For me, I don't know."
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