This was achieved by moving and reshaping the fuel tank, building a more compact engine (see diagram (4) in top picture) and placing the mounting point for the rear shock inside the frame - all while keeping the same wheelbase (see diagrams (2) and (3) in middle pic).
Meanwhile, frame rigidity was optimised by removing
a chassis cross member (see diagram (2) in top picture).
Results of the 2005 development programme.
In terms of engine performance, the initial 2005 powerplant used at the Jerez season opener produced more top end power compared with the 2004 version, with further engine developments - introduced later in the season - increasing top end even further (see diagram (1) in lower picture).
But in some cases less outright engine performance was needed, which is where the 'torque control system' helped improve drivability. The system restricted top end torque in all but sixth gear, although it wasn't needed lower down in the engine powerband (see diagram (2) in lower picture).
In terms of top speed, the 2005 engine produced an average increase of just under 5 km/h from seven of the first nine races of this season, with the biggest top speed increase seen at Mugello (approx. 7.5 km/h). However, top speed fell by around 3km/h at both Assen and Brno (see diagram (3) in lower picture)
Results for fuel economy showed an average increase of 8%, with consumption well above 5 km/litre at all events listed (see diagram (4) in lower picture).
The 2006 YZR-M1.
So how will Yamaha make the 2006 M1 - the last incarnation of the YZR-M1 before MotoGP engine capacity is reduced from 990cc to 800cc - even better again?
A prototype version of the new M1 made its official track debut at Sepang last week, where - apart from the never ending search for greater engine performance and tyre grip - factory riders Rossi and Colin Edwards were impressed by its increased stability, suggesting that similar priorities to those which worked so well for 2005 are again being pursued...