A bike is great to have but best to buy one of the local Hondas for around Rp40-80,000 and then resell it later for maybe half that. Rent them on Bali or Yogya, Rp1000-2500 per day. In his book, S.E. Asia on a Shoestring (1975), Tony Wheeler claims that taking a lightweight (because you load and unload it frequently) machine through the islands is quite feasible (he did it) and well worth it. Freighting costs aren't that high and petrol is cheap. Top up at Pertamina, they sell the cheapest petrol. Tony says that you need a carnet which is a deposit you leave with an Automotive Association at home to ensure that you don't sell the bike in Indonesia. So you don't get bogged down by hours of paperwork at the customs dock, try just driving right off the ship and right through the gate saying hello to everyone without stopping. You might make it.