T40 torx security bit. See the pics in the recent thread courtesy of that nice Mr Six5.
http://www.tlzone.net/forums/suzuki-tl1000r-tl1000s-forum/135930-c42-error-could-caused-battery.html
http://www.tlzone.net/forums/suzuki-tl1000r-tl1000s-forum/135930-c42-error-could-caused-battery.html