I believe that the fan is part of the camchain problem. The fan itself weighs 0,2 kg, with a lot of that weight around its circumference. Putting that kind of weight on the end of the camshaft, spinning at up to around 5000 rpm's, can surely be no good.
Every time you close the throttle the camchain will try to reduce the speed of the camshaft, and the fan will resist due to its weight, loading the tensioner and slacking at the guide side. Every time you open up the throttle the fan will also resist against this, putting a load on the camchain. This can make the camchain slam from side to side, overpowering the tensioner. Also when idling, or at certain speeds, chatter could occur.
Further on the fan robs power, and puts even more load on the camchain because of that.
I think electric is the way to go...
Just my thoughts,