Just got a new (used) s40 and am beginning to think of the upgrades I wanna get into.  One of the first on my list is an HID conversion.  I know they're more common on sports bikes but I like the safety aspects of it for my s40 too.

My question though... where is a good place to mount the ballast?  

I'm also trying to decide between a 4300k and 5000k bulb (as seen on this link http://shop.3bspecialties.com/05-08-Low-High-Dual-Filament-HID_c1296.htm;jses...).

i have thought about the HID also..i went with a higher K halogen(same watttage as stock but lots brighter)
sylvania i think..along with mr11 led bullet runnnig lights I can see and be seen just fine..
my concerns besides the ballast placemet(there are some that will fit in the headlight housing)is the nature of the ls 650 elect start up sequence..the head light comes on when you turn the key then goes off when you hit the start button then on again..
hids have a high inrush current till the gas ignites then very low current when lit..not sure how our on/off/on would affect the ballast in the long term, expensive if it fails..could add a switch to isolate the hid from the starting circuit till bike was running...

btw why are your posts RED??