Rossi's M1 to keep inline-four engine.

Ever since Valentino Rossi's two-year Yamaha deal was confirmed, speculation has grown as to whether the Japanese manufacturer is planning to build an entirely new machine for the Italian, perhaps without their traditional inline four-cylinder engine.

Such speculation was partly fuelled by Rossi calling his new challenge a 'little bit crazy', which some have interpreted as meaning more than 'just' moving from Honda to Yamaha.

The 2003 M1 has struggled to match the horsepower outputs of leading V-configuration engines, campaigned by the likes of Honda (V5) and Ducati (V4), and - although improvements were made - the M1 was only eighth fastest through the speed trap at the season ending Valencia Grand Prix, behind both Ducatis and five Hondas.

Despite this, Yamaha has faith in its choice of powerplant design, although the 2004 M1 will, as expected, see both the chassis and engine substantially modified as they try to keep Rossi on the top step of the podium.

"As you are aware we have just tested a prototype chassis in Valencia, and a revised engine is currently being completed in Japan, based on the inline-four concept," a Yamaha spokesperson confirmed to Crash.net.

Yamaha's highly complex M1 has taken victory in two GPs since the MotoGP class was formed in 2002. Both wins were delivered by Max Biaggi in its debut season, and the machine claimed a best finish of third this year.

The Toyota F1 team are rumoured to be helping Yamaha with electronics on their 2004 racer.