Well I was going to say here that Halim is a great place to bike but after a recent trip there(Sep'98) it appears a lot of the good tracks are overgrown with grass and prickles. While there is still a few nice rides and it is probably still worth a trip(if only to see the Model aeroplanes and Helicopters crash at the JAC (Jakarta Aeromodellers Club) the best bit of Halim needs some serious wipper snipping. This was the speed/jump track (oversize BMX track)). One farmer is even planting Casava on the tracks. All bit of a pity really.
If you still want to go then to get there you head towards the Halim Golf course. That is go to TMII via the ring road(Taman Mini) and turn right after TMII at the big movie billboard(traffic light). Keep going straight past the white hospital, past the Halim Golf course turn off and take the next right straight after the traffic lights. Go straight until you get to a sign that says "Skadron 425" or something like that(the airforce base. Turn left and go to the end where you will see the JAC sign. Follow the little dirt track to the JAC shelter.
This is the aero modelling JAC site Nice bit of single track Somewhere else