The 1,600 km from Urumqui, to Kashgar, Xinjiang took 3 weeks. The road first goes to the minus 150 meters desert oasis of Turpan then heads west, paralleling the Tian Shan mountain range, to Kashgar. Our trip in May had 15c days and 5c nights, but winters are bitterly cold and summers have temperatures over 35c. Food is readly available in towns located 150 km apart on the frequently traveled Urumqui - Kashgar road. Foreigners can take buses between Urumqui and Kashgar.
Cycling is probably technically illegal but can be done on the sly.
From Kashgar the road went south for 500 km to the town of Yeching, which is the last urban outpost before the road crosses the Kunlun mountains. Yeching has a large military post and was off limits to foreigners in 1986. You could leave the road on a moon lit night and bypass the town and road checkpoints in a few hours. From Yeching the road climbs in about 150 km to the Kunlun pass at 5,000 meters. On the south side of the pass is the rough outpost of Mazar, which serves as roadend for expeditions heading to the Chinese Karakorum and Mt. K-2.