What can cause a 2000 Honda 350 rancher ATV not to fire?

It is either one of your electric parts gone out such as CDI or the coil but my 2002 Honda rancher 350 wouldn't fire and I sprayed WD-40 on the electrical connectors and then it started to fire. If you have been in lots of mud this might have been caused. Make sure the switch is off when unplugging the wires (Honda electrical system is very sensitive).