From MotoGP.com:
HRC confirm Stoner crash in the Suzuka 8 Hours was due to throttle mechanical issue.
Honda Racing Corporation has carried out a detailed analysis following the crash of Casey Stoner in last weekends Suzuka 8 Hour race.
Checking the throttle, which is a particular specification for Endurance HRC Factory bikes, and different from the standard throttle used on the Honda CBR1000RR road version, a malfunction was discovered related to the throttle cable.
This kind of problem hasnt arisen before, however, HRC will cease using this throttle specification and will design a new one to be used for Endurance races.
HRC would like to apologise to Casey Stoner and thank him for the effort he made in attending the Suzuka 8 Hour event.