Many guys at
KZrider.com - Home have done a very simple wiring modification using a 40 amp automobile relay to bypass the aged wiring on these older Kawasaki's. To see if your bike could benefit from this, remove the gas tank, and with a fully charged battery, turn on the ignition but don't start the engine.
With a meter, check the primary input terminals on the ignition coils(smaller wires) it should read battery voltage or real close. If it's down around 8 volts or less, your bike has a voltage drop that will affect the spark energy output.
After doing this modification, your bike should be much easier to start with increased combustion efficiencies. The website
www.wgcarb.com has instructions on how to do it along with parts needed. His website also has a similar forum for questions.