Brother im from shigar skardu Baltistan we went to skardu from Islamabad on Road Prince 70, United 70, and YBR 125G at 12 June 2018.
You should Travel between June to August because after that Roads are very slippery due to Heavy Snow and babusar top is open only for three months the other route is from kohistan which is open always but it is very long route more than 6 to 8 hours than babusar road following is the route details
From islamabad to skardu via Muzaffarbad, Ghari Habibullah, Balakot, Naran Kaghan, Babusar top, Chillas, Astore, Chillim, Deosai, Skardu it took total 18 hours for us bike riding 620 KMs