Yamaha team boss Lin Jarvis says the MotoGP outfit does not need a "revolution" to get back to winning regularly in 2019.

Yamaha revealed a dramatic new look for the upcoming campaign on Monday at a Jakarta launch event ahead of the start of official pre-season testing in Sepang on Wednesday.

The manufacturer is looking to rebound from a difficult 2018 season in which it won only once all year, with Maverick Vinales ending the firm's worst-ever premier class winless streak in Australia.

That result came in a short period of improved form for Vinales and Valentino Rossi towards the end of the year, which Jarvis said means Yamaha does not require a total overhaul if it is to get back on terms with its main rivals Honda and Ducati.

"Honestly, we don't need a revolution at the moment," said Jarvis. "We need strong evolution.

"At the end of last year, we were very close.

"We need to be perfect in every area. If we bring revolution now, we may lose our base.

"There's nothing radical [about the new bike]. We spent most of the time in [post-season testing at] Valencia selecting our engine, so now we will deliver one or two choices that will be fine-tuned from Valencia."

As well as the change of livery, Yamaha will also start 2019 with a new project leader as Takahiro Sumi replaces Kouji Tsuya.

A European test team headed by ex-Tech3 rider Jonas Folger and several organisational changes relating to how Yamaha's Japanese and Italian bases interact with each other have also been introduced.

As well as the latest specifications of engine, Jarvis added new electronic and chassis "solutions" are among the items to be tested at Sepang this week.

"It's a very important test for us, it's crucial," said Jarvis.

"A lot of people asked me last week in Italy, 'How will you be doing this season?' And I said, 'Honestly, I hope good, but I don't know'.

"Until we go to Sepang, we don't know how good our competitors are. Maybe we can judge ourselves not so bad, but if our competitors make a big step, maybe we can't be competitive."

Rossi, who has not won in MotoGP since the 2017 Dutch TT, spent much of last season calling for Yamaha to increase its resources and make a major step instead of incremental improvements.

Asked what he made of the changes Yamaha has made for 2019, Rossi said: "In the last two years, our opponents very much changed the way to work.

"Ducati especially changed a lot, putting more people in different areas and trying to organise the team more like a Formula 1 team. So we have to follow [that example].

"Looks like some things have changed in Yamaha and we have some new Japanese engineers, but also some European and Italian engineers from Milan, from the headquarters.

"It will be very interesting. I think we can be strong, but we have to wait."