I'm trying trying to remove the fill port dust cover sleeve on my Taipan Mutant. I have removed the grub screw/set screw, but the sleeve will only slide about 1/4". On my Taipan Veteran when I remove the grub screw/set screw the fill port dust cover sleeve just slips off. Any help would be greatly appreciated. I'm trying to get to the gage which I think has a slow leak.