Now i am sure that most of you know you can buy decent LED replacement bulbs on eBay, that will replace a 21w bulb. However that is not as much fun as building your own units.
Now this is a very simple method using cheap materials. as always i try not to over complicate things,
-4 8mm 0.5w strawhat LED's per light
-a piece of semi-rigid plastic to cut 35mm discs out of (i.e. ABS)
-soldering iron and solder
-drill and drill bits
-small nut and bolt (M4-M6)
-heat shrink sleaving 4mm
Step 1: Remove the light unit and dissasemble
Take the unit of the bike (or car!) and strip it down so you can freely acsess the lamp mounting. it is important to note the inside diameter of the collar (not the hole) for later. have a look ahead if your not sure what i mean, as it will become clear.