That was it! After hours of tearing that four wheeler apart checking wiring, fan, etc., the resolution was the oil sensor was unplugged. Best I can say was a stick got up in there and popped it loose. I was able to get to this sensor by removing the factory skid plate that was attached with about 6 - 8 bolts. Once that was removed, the wiring and sensor was easily visible on the rear of the engine a bit higher up and further back from the oil drain plug. I plugged it in and ran it. The four wheeler ran forever before the fan kicked on...I assume that when all the sensors are plugged in and working correctly it would take awhile to overheat the engine!
Thanks for all your help Trikemaster! I don't know if I would have been able to get through this without your help!
Chris