The voltage rectifier on my King Quad started smoking and melted the insulation off of one of the wires. I ordered a new rectifier, installed it and it gets pretty warm after just a few minutes. I'm headed back out too check ground connection. If the ground is good what should I check next.

 

Check your stator. They fail one of two ways.

1- Stop putting out as much voltage/amperage > weak/no spark
2- Put out more voltage/amperage > Blow rectifier and CDI and headlights

Check your manual for an ohm reading you should get from it, if it is out of spec replace it. Whatever you do, DO NOT run without the voltage rectifier, you might catch something on fire.
Might want to check your battery as well to make sure that is putting out good voltage. Might be overdrawing from the stator to the charging circuit. Electrical problems are hard to troubleshoot. Just make sure you dont fry anything on accident. Good luck.