Let's clear the air here.
The kit supplied spark plug wire has a solid metallic core. It is either copper or steel wire. Yes, it is true that the outer layer, or insulator, is of poor quality and prone to cracking and allowing current to 'leak' or jump to a grounded surface. Nevertheless the conductor, or core wire is better than what you'll get from most auto parts stores or even the junk yards today because most of what you'll find is resistance wire. The automobile factories started using resistance wire TVRS, back in the late 60s to reduce electrical interference with radios. Later cars rely on it to eliminate electrical interference with sensitive electronics such as the computers all cars today rely on.
The chinese 2 stroke engines are not equipped with high voltage ignition systems. Any resistance between the voltage source, the CDI, and the spark plug will reduce the voltage needed to arc, or make a spark to ignite the fuel charge in the cylinder.
Resistance wire, of any brand, is made to work with ignition systems that produce several times the voltage produced by the CDI which comes with the engine kits.
Yes, it is true that some so called 'high performance' ignition wire will work and even the wire you get from the auto parts stores, will work. But, it only takes a good ohm meter to measure the difference in resistance between a solid metallic conductor and a wire made for today's cars to see the difference.
I want every volt produced by the CDI to go to my plugs and not be wasted by trying to squeeze through a cotton string impregnated with carbon before it gets there.
If I was running a high performance automotive ignition system that produced several hundred thousand volts I might consider using resistance wire. However I am relying on a simple and cheaply made ignition system, the CDI, to fire my plugs and I give them all the help I can.
Copper core wire, soldered to the spark plug connector and securely screwed into the CDI is what I recommend. Anything else is a compromise.
Tom