In the clutch master cylinder, or in the gear case? If in the clutch master cylinder, you need to use what it tells you to use, as I believe there might be a year or two which used DOT 4 brake fluid.
But if gear case, I use a blend of ATF Type F and motor oil. 75% ATF/25% 10w30 in the winter, and 50/50 ATF/10w30 in the summer.
Most ajp clutches are mineral oil (I have been using 2.5wt fork oil as a substitute without any issues) but there are other year's (I think 2012 was one of them) that had a different clutch so best to check the cap of your master reservoir