Did you try to tune the gear ratios?Top speed doesn't match reality, 6th gear is too short.
I got 312 on Mugello with Yamaha and 317 with Ducati, while real speeds of this year were 344 for Yamaha and 354 for Ducati.
This problem happens for each track, with different top speeds between the tracks (i think gear ratio is automatically changed by the game based on the track) but for every track it is always too slow compared to real speeds.
Are you trying in the time trial or in a race? Because i've putted the top speeds based on race table of the MotoGP site. This game introduced the dragging effect now. So now we can drag behind another bike to have more acceleration and less air resistance, resulting in a bigger top speed.
I've made the top speeds based on the Qatar track, dragging behind others bikes, so there are the trully top speeds, if i've making the top speeds based only in the force of the bike, in the drag situation you will put unrealistic top speeds...