Yamaha's 2017 MotoGP design will not be the mooted revolution

Massimo Meregalli, Yamaha's technical director, said at the end of 2016 that the firm was slightly behind schedule with the development of its '17 prototype because it would be a "revolutionary" bike.

But a high-level source within the team has suggested the new machine - to be unveiled at title sponsor Movistar's headquarters in Madrid on Thursday - will not be as dramatic a step as had been hinted.

Only the engine is a completely new design for 2017, with the rest of the bike based on its predecessor.

"In the end, if you are not coming from a very serious problem, what the factory does is change a lot of things but without modifying the bike's philosophy," a senior Yamaha source told Autosport's sister title Motorsport.com.

"The base of the 2017 bike is the same as in 2016, with a different chassis, a different swing-arm, a different engine, different suspension and everything different - but without ruining the philosophy of the 2016 bike."

Yamaha riders Valentino Rossi and Jorge Lorenzo were beaten to the 2016 title by Honda's Marc Marquez.

But the Yamaha was widely considered the stronger bike, with some early-season engine failures among its only weaknesses.

The source added: "At Valencia [in the post-season test], a few new things were tested, but it wasn't the final 2017 bike and it wasn't the one we'll see at Sepang.

"There, we'll have a prototype based on all the 2016 data, plus the data gathered in Valencia and Sepang [where Yamaha tested privately in November].

"But I'm sure the bike will continue to change after the remaining pre-season tests."

With Lorenzo having left for Ducati, ex-Suzuki rider Maverick Vinales has joined Rossi in Yamaha's 2017 line-up.