Thanks for the responce;
Well the border between Pakistan and Afghanistan is closed for crossing since long due to security reasons. Now the only possible route is from Pak to China via Khunjerab Pass, from there enter to Kygyzstan and then to Tajikistan. Secondly foreigners can't cross the border between China and Tajikistan. Moreover drivers/bikers also have to deal with driving in China, which can be a nightmare for foreigners.