What bike is it in? If it's rubber mounted, you can typically tug on the motor a little bit enough to squeeze your allen in there. It is handy to trim the allen down first, though. Check out Griots garage webpage. They have a handy little tool set with a bunch of different tips that has saved me in numerous tight spots on my Evo's and TC's!! It has a screw driver adaptor and a ratchet adaptor.
96 WIDE GLIDE
94 ROAD KING
IF EVERYTHING IS UNDER CONTROL, YOU'RE GOING TOO SLOW!