Thank you everyone :)
Just for a note, I ALWAYS use a halter and lead rope, I was just experimenting. I wasn't free lunging him, just getting him to follow me, move his back legs, back up and stand still for a brush :)
He has NEVER run up to see a quad... He just thought It was Gerald and that meant lots of cuddles, licking molasses off his shirt and possibly beer :P
After I chased him down and got his attention back (which really didn't take too long) he didn't worry about the quad any more and I was still able to play around with just the lead rope, like I said, I was just experimenting and its not how I handle my horse when Im asking for more work :)
Thank you so very much to everyone who replied, I was very curious as to what his behavior meant