99% of the time, it is the main starter relay that buzzes (the one with the integral 30amp fuse) and 99% of the time, it is because of the battery. If you can check to see if it is this relay, post back and we can take it from there.
Did you discover the source of the problem. I'm having the same with my 800. Have replaced the solenoid with the 30 Amp fuse and the battery is brand new but still the buzzing and eventual turn over.The buzzing was coming from the relay under the seat in the junction box. This is not the one lower down with the fuse. I replaced the entire j box and I'm still getting the buzzing from the same place. At first I was thinking battery which is why I had it tested, but it seems fine. Once the starter starts to spin is springs to life and sounds normal. There no dimming of the lights, and it's not behaving as if there's a battery issue. Is that other starter relay a common issue with our bikes? If so I think I'll probably pop that out next. I'm thinking it'll be cheaper than a starter. Does this sound like a reasonable course of action?
Neither Vulcan1500 or Alex J have been seen on the forum for years, and neither since posting in this thread.Did you discover the source of the problem. I'm having the same with my 800. Have replaced the solenoid with the 30 Amp fuse and the battery is brand new but still the buzzing and eventual turn over.