Long and the short of it - wind the throttle on and bam engine's dead. Usually when I've just hopped on, after warming it up. Had the same problem a few months ago and it went away by replacing a battery that was on its last legs. I'd guess the same problem this time round but I'm fairly sure that these things are meant to last far longer than a few months with near daily use. I'll be picking up a multimeter on the way home so I can properly diagnose the battery before forking out for a new one. I'm ruling out a loose connection with a battery terminal because lights/dash/whatever are still running when the engine goes. It doesn't clutch start either when this happens, I've got to pull the clutch in and whack the starter which fires it up instantly. Is it possible the HIDs have done a number on the battery (it's a yuasa ytx, possibly 14-bs)? Only recently put them back in because I didn't have em mounted properly initially and didn't have the time to pull the front end apart, probably about 2 weeks ago, and this has been happening for around a week. It usually fires up on the first or second crank when cold. It happens less the longer I've been riding, but the tacho does seem to dance around a bit under heavy throttle. So yeah, is a rooted battery doing this or is there another problem?