The FIM has released a short statement that seems to indicate where the line will be drawn in terms of using production motorcycles in the MotoGP (and Moto2) World Championship.
"On the occasion of the San Marino Round of the 2011 FIM Superbike World Championship in Misano (ITA), and with reference to the interviews recently published on some motorsports web sites, FIM President Vito Ippolito reiterated what has already been stated several times:
"Any complete motorcycle model derived from series production, homologated or not for the FIM Superbike/Supersport/Superstock is not eligible and will not be accepted in the FIM Grand Prix World Championship classes," said the statement.
The key words are 'complete motorcycle'.
In the early years of the 990cc four-stroke era, which began in 2002, even modified production engines were not allowed in the premier-class (see the problems suffered by WCM in trying to use an R1-based engine).
In other words, grand prix was only for 'complete' prototypes.
MotoGP is switching from 800cc to 1000cc (Superbike size) engines next year, with a new class of Claiming Rule Teams (CRTs) also being created to help boost the present 17-rider entry.
The CRTs won't be able to afford a complete prototype – as currently raced by Honda, Yamaha, Ducati and Suzuki - and the 2012 technical rules pave the way for CRTs to use lightly-modified production engines, inside a prototype chassis.
The FIM statement looks to confirm that such a combination will be allowed in grand prix.
World Superbike and Supersport will remain the only FIM road racing world championships for 'complete' production bikes, although the exact definition of 'complete' remains open to debate...