About the voltage regulator effin' up the running.... It's true.
Got a '97 king quad.. a freebie fixer upper.. Got it to start, and run, etc.etc. But, once the battery was fully charged, it'd run O.K. at idle, then buck and jerk and run like a bag of hammers. I couldn't find the problem to save my life. I had the meter out to try and get the power port 12 volt thingy working, and the meter showed 18.2 volts..
Google quickly let me know that this was WAY to high and would have " adverse effects" on ignition, headlights, etc. I changed the voltage regulator, and it's been all good ever since. On;y crappy part was having to take off the plastics to get at it. At the end of the day, I couldn't get the old one out ( rusted mounting screws), so I just stuffed it in there, and zip tied it into place.
When you put it back together, be sure not to disturb the trigger wire to the starter relay.
Don't ask me how I know this..