The present study was conducted to investigate the role as determinants of the major mechanical constituents of cleaning Egyptian seed cotton (extra-long staple) Giza 86 cultivar was harvested by cotton picker during 2005 season at El-Karada farm, Kaferelsheikh governorate. The newly cleaning extractor was operated and tested with four saw drum speeds 7.06, 8.63, 10.20 and 12.56 m\s, four levels of feed rates 10, 12.5, 15 and 17.5 kg/min and four levels of moisture content for fiber 11.2, 9.8, 8.7 and 7.9 %, respectively, to determine its effects on some mechanical properties of cleaning seed cotton such as: seed cotton strength, g/tex, seed cotton elongation, %, seed cotton trash content, %, seed cotton wastage, %, and seed cotton cleaning output, kg/min. Results showed that using the new local cleaning seed cotton extractor produced high values of seed cotton strength and seed cotton cleaning output. While, it producted low values of seed cotton elongation, seed cotton trash content and seed cotton wastage.