Runner fx cdi ignition controller wiring question

Hi guys, recently picked up a more or less standard runner fx (drum) to play with. It's been bodged here and there, i'm currently putting the wiring straight.
Problem is an extra wire, currently disconnected, it has an inline 7.5A fuse and runs to the red (power in from generator) wire of the cdi. Is this a common mod? I'm guessing the idea is to supply 12v regardless of the generator output at low revs.
I haven't checked the ignition switch logic yet but I'm bothered that the battery may drain with this extra wire connected. Also bothered about potential cdi damage. It looks like replacement unit.
Any thoughts??
Cheers,
H

 

I would isolate it for now, get the rest sorted, get the bike started, make sure everything works as it should, including the battery charging at 14.2v when running, then solve that one. It may be a simple cut out switch solution, but I'm only guessing.

 

Thanks Steve, that sounds sensible. It had a bogging problem when I bought it and it couldn't be revved, as soon as the clutch engaged it stalled. Was wondering if this was attempt to cure the problem.
I've found a few other causes though, not least the intake rubber was split. Also the fuel pump vac hose had been cut and badly rejoined with an old tyre valve (!). Air filter is also gunged up, I expect the carb will be too.
Cheers
H