My daughters 87 lt-80 has an issue with breaking up under load and higher rpms.
The bike will shut off by simply touching the plug boot or wiggling the coil wire, i have replaced the plug boot and also the wire and the connections seem fine.
This bike has the cdi and coil in one unit and is kinda pricey so i was hoping someone ran into this before i spend $180 for it.

 

That sounds like the stupid spark plug cap. A terrible design IMO.
Try duct taping the spark plug cap to the motor and see if that helps.

 

Ok, i will give that a try.
I have changed the cap twice, i trimmed the original wire and reinstalled it, then i replaced the whole wire and cap with a new 8mm wire from a car. It seems better with this setup on but it still cuts out.