Factory Yamaha MotoGP riders Jorge Lorenzo and Valentino Rossi will not have the factory's new seamless shift gearbox for this weekend's Czech Republic round.

Both riders were delighted with the technology, versions of which are already used by Honda and Ducati, after trying Yamaha's design for the first time during a private test at Brno earlier this month.

The special gearbox not only shortens shifting time, but more importantly increases stability, with the motorcycle less 'upset' by the gear changes.

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The shorter shifts are achieved by engaging the next gear before the present gear has been disengaged, but the exact methods used remain a closely guarded secret.

Yamaha did not feel ready to use the gearbox at Indianapolis last weekend, with Lorenzo and Rossi's hopes of a Brno race debut now also scuppered.

"It is the big question that me and Jorge ask the Japanese every morning! But still [the seamless] is not ready." said Rossi at Brno on Thursday. "I hope as soon as possible, but we still don't have a date."

"I think the seamless is very important to try to be faster, especially over a race distance," added the Italian, when questioned about the significance of the new gearbox. "But I also think it is not enough. We have to continue to work on the bike, because we have some other problems compared to the Hondas at this moment."

Putting aside any reliability fears, with both Lorenzo and Rossi having already opened the fourth of their five engines for 2013, it may not be technically possible to introduce the new gearbox until the closing rounds - unless it is compatible with the engines already in use.

Lorenzo is third in the world championship, 35 points behind the leading Repsol Honda of Marc Marquez, with Rossi a further 23 points back, in fourth. "I hope we do not need it [to beat the Hondas] because we do not have it!" said Lorenzo of the new gearbox. "But of course it would be a good advantage for us."

Meanwhile, both Rossi and Lorenzo played down the advantage they will gain this weekend from testing at Brno.

"It's a small help but doesn't make much difference," commented Rossi. "When we came here we tried to work very much on the seamless. We used a lot of time to try and improve the system.

"And afterwards, for sure we worked a little on the set-up, which may be a small advantage tomorrow. But I don't think we can keep this advantage until Sunday. Also it was 35 degrees and now it is 15 degrees lower."

Lorenzo believes Honda remain the favourites, but expects to be more competitive than at Indianapolis, where he finished third to Marquez and team-mate Dani Pedrosa.

"I don't think we're the favourites at any race at the moment, but I think we have more options to win here than in Indianapolis," said Lorenzo. "This track has no first gear corners, a lot of changes of direction. So I think it will be good for my riding style and the Yamaha.

"But in racing you never know, so we must wait until first practice to see our level.

"These three races in three weekends are very important for the title. We didn't crash at Indianapolis and got a podium after some weeks without it. Now, if we want to win this world title, we have to start to win races again as soon as possible. At the moment it's not so simple, but we're going to try.

"I get better physically every weekend and I think these three races are good for me to rebuild fitness," added Lorenzo, who broke his collarbone and underwent two rounds of surgery in July. "It is not only the injuries but my physical condition that suffered because I could not train. Now I'm getting better every day."

Brno is round eleven of 18.