There have already been discussions on building a superior CDI, but what about the stock Chinese CDI? While it's rather poor design to begin with, the simplicity and semi-decent functionality make it an attractive electronics project. I don't think that nearly enough is known about the stock CDI, so I think it's great that this topic has come into discussion.
Rohmell on motorbicycling.com(the same Rohmell who made custom CDIs) created a thread about learning more about the stock CDI and possibly building a new one.
A warning to those looking to mod their motorized bicycles:
Most, if not all, of the hacks and mods featured on this site were made by individual hobbyists. If you are new to working with 2-stroke bicycle engines, please by aware that there's a possibility that a mod featured on this site could seriously damage your engine. Please don't try any mod from this or any other site unless you fully understand what you are doing. The owner of this blog will not be held responsible for both material and bodily damage caused by performing a modification featured on this blog. Also remember that opening up your engine may void your warranty!