If you look carefully at my post 522 you will see that the 1905 Flyer was lighter than the 1904 Flyer because the Wrights removed 70 lb of ballast used in the nose of the 1904 Flyer to improve the C of G...
Hence...
The engine stayed the same as the 1904 aircraft and the weight was decreased to 860 pounds by eliminating the iron bars (70 lbs ballast in 1904 a/c) . The 1905 aircraft could be flown until the fuel tank was empty; staying in the air for more than a half hour, flying nearly 25 miles around Huffman's farm, executing turns and figure 8's, and flying more than 50 feet off the ground. The brothers now had a practical working airplane and began to market it to the War Department.
1903.....750 lbs (inc pilot) with 12HP motor - 505 sq feet wing area
1905......860lbs (inc pilot) with 18HP motor - 505 sq feet wing area