The muffler is too loud to hear the fan until I turn the engine off. It is running then. I had thought about that, but, when my friend got the bike, who I got it from, it had the problem then (2 years ago) just not as bad. I had also thought about something internal, like the headgasket, but the bike has had about 2,000 miles on it sence he bought it and nothing else seems to be effected. I did recently find about 15 to 20% of the fins on the radiator bent. Most of them in front of the fan. Mabe it is a combination of a lot of little things and it will run right when it is back together.
Just thought of something. It takes just over two quarts of coolent. When I checked the level it was full, or it seemed like it. When I drained it two quarts did not come out. Could there have beed a big air pocket in there all that time?