I completely agree with the upkeep and not needing all of the tools out there. I've actually never busted a chain either.
Now if it came down to the absolutely essential needed gear for a race or more extreme trail riding I'd carry this:
Flat head for carb adjustments.
Spark plug if any chance of fouling one
Plug wrench to obviously get the plug off
Zip ties for the chance that something snags or something
Rag to clean up any mess of wipe your goggles
Having wrenches, ratchets, pliers and masterlink and stuff wouldn't be needed if you keep up on maintenance. I'm just trying to keep this down on size and weight. I don't plan on using it and would ultimately like to just forget it was there. It'll kind of be like a first aid kit. Most likely not needed but handy if you do.
This being said, I'll have larger tools and such in my tacklebox. Things like flywheel puller, lug wrench, cotter pins, bolts, washers, nuts, hammer, larger wrenches, woodruff keys, fuel lines, spare set of tires/rims, rags and fluids.
Then after this is all said and done I will be weighing my quad wet with all tools on it. I'll list what I have to a "T" so people have an idea instead of guessing or comparing. I know this has been debated on for years and I'll be starting a thread with facts. Just letting y'all know in advance.