This is one of the more unique clutch mods I've seen. The clutch can be a pain to disengage without a pulley, but this hack would theoretically make it a bit easier to pull in the clutch.
Rounding off the edge of the half-circle might give the clutch more of a dropoff and make it easier to ease in/out. If you're one of those people who slips the clutch to start from a complete stop, this may make that process even easier!
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!