Complex sentence: It was typically held in September, the month before Australia's other main endurance race, the Bathurst 1000, however the race was not run in 1966,1967,1999 and 2000.
Split into simpler sentences: It was typically held in September, the month before Australia's premier endurance race, the Bathurst 1000. The "500" was not run in 1966,1967,1999 and 2000.