I have not had that problem, but I think that it is odd that you have the same problem with both machines. That makes me think that your problem may be caused by similar riding or storage conditions. I would check all electrical connections on both machines. I think it is very possible that you will find corroded connections and grounds on both bikes. A poor ground can be bad for the lifespan of a generator.
Yours truly, sincerelly, love always, Josh aka The DirtDemon.