kdxquebec,
The bulb that comes in the bike is a 30/30 watt quartz halogen, it won't melt the plastic. I have a 55 watt quartz halogen and it hasn't melted. But I wouldn't go and higher.
91kdxrider,
There's the two different coils: the bottom one is your ignition and the top one is the lighting coil, you only need to rewind the lighting coil. Remove the stator assembly (ignition coil, lighting coil, back plate), there's 3 bolts holding it on. You'll have to take the gas tank off and disconnect the 3 wires to completly remove the stator, making life easier. With the stator off the bike, take the 2 bolts out that are holding the lighting coil on. Notice the crimped/soldered ring terminal attached to the right bolt, that's the end of the wire.
There should be a nylon zap strap around the coil, cut it off, as it holds the connection between the insulated wire and the winding wire in place. There is a piece of tubing protecting the connection, cut it off (you'll need a new a new piece of tube). Cut the connection, try not to cut any insulated wire. With the wire cut, the coil is able to be removed. Now the coil can be unwound (I recommend doing it outside or in the garage because the plastic resin gets everywhere). Notice how the wire is wrapped around the black plastic retainers.
Before you start to wind the core, leave a generous piece of wire that attaches to the insulated piece, you can always cut the wire down after your done winding the coil. When your winding it, keep the turns as tight as you can, and try not to kink the wire as it is harder to wind and keep the turns tight to each other. On the stock coil, there's plenty of room to put more windings on, at least 3 more rows (I forget the proper name for a row). There's enough room that you can build the rows up above the black retainers. I believe I put 8 rows on total, 2 were above the retainer. With rows above the retainer, the side windings will want to slip off, I used dental floss and wrapped it around the coil (length ways). Then take it to a rewind shop and have it dipped (it keeps out moisture, secures the dental floss and helps hold the winding together). Last of all, when you solder to the coil wire, use a knife and scrape the fine coating off.
If you need any clarifying just ask,
Warren