Hmm, good question. I wanted to change all the filters on my 99 MXZ so I went to the dealer and he asked me if I wanted the external filter, or the internal screen filter. He said the external is all you should really need to change. So the other night I went looking for it, and there doesn't appear to be one. I looked on the microfiche, and it doesn't even list one???Where is the fuel filter located? Can't seem to see one? 98 ski-doo formula deluxe 583?