is the 2005 AC 500 slower then the 2004 because it weighs about 50 lbs more

 

Well, I'm not sure if that's the dry or wet weight, but the '05 has a 6.5 gallon gas tank and a locker, so that will account for a few pounds, anyway. Maybe the chassis is designed a little differently due to the gas tank location and that might have added weight. The new plastic and slightly bigger racks probably adds something as well.