After having my fan bearings lock up on my B7100, I proceeded to remove all the front sheet metal and radiator. I am looking for the name of the designer who put that nice stud/nut that is next to impossible to get to. I was able to bend up a cheap 10mm openend I had laying around and was able to get it removed. The fan housing bearings were shot and one in pieces. I was able to get some replacements from McMaster Carr for $5.34 apiece and have it back together. Much better than the cost of a new fan/dyno. I think that the prior owner that cracked/overheated the head along with melting the solder out of the top of the radiator did not check the fan bearings. I believe the grease was melted out of the bearings and ran dry for awhile. One nice thing is that the replacement head has a port for a temp gage in the head. Putting the fan back on was a bit of a hassel but stuck the nut on the tip of my finger with rtv and fingered it onto the stud. Don't laugh, it works. All back together and waitng till later to restart.