I just finnisched the first part of my Borneo-Tour (in Okt. Nov. 2012)
From Banjarmasin in the southeast to Kuching in the northwest. Traveling clockwise I took following route:
Banjarmasin to Sampit(415km); to Pangklanbun (245km); Nangabulik(110km); Kudangan(110km); Nangatayap(75km); Sandai(40km); Tayan(190km); Pontianak(116km); Ngabang(150km); Entikong-Bordercrossing(150km); Kuching(100km)
Altogether close to 2000km and it take me 8 riding days.
Good paved road from Benjarmasin to Kudangan appart from some short construction areas and a few large pothols. Around Kundangan the road is new, but bridges are under construction. From Kudangan to Nangatayap the road is paved till past the West-Kalimantan-Province border. Then there is a stretch of 50km earth road winding through the jungel. Nice and mostly smooth to ride during dry weather. But seems to be slippery/muddy when wet. From Nangatayap further north to Kuching the road is paved, and in good condition.
Small scooter or overloaded Big-Bike even midsize Truck can travel all the way. (Dryseason)
There are enough Gas-Stations on the way, and if not (No open Stations between Nangabulik and Tayan) in every Village you can by Petrol out of glasbottels from private shops. So no worrys.
Some roadsighns, helpfull people everywhere and a Reise-Know-How map, had no GPS-Map
40 minutes in total. You need a Carnet.
In the bigger citys are hotels. In between I slept in Nangatayap (basic losmen) nearh the Intersection wehere you have to turn east (traveling nort to south) GPS:1°30'57''S, 110°33'49''E and Tayan (Hotel Marinas GPS:0°2'7''S, 110°6'51''E). Ferry crossing in Tayan is some kilometers east of town.
Hope this Information will help other travellers on this less traveld route.