Chain problem

I noticed a repetetive whirring coming from somewhere near the front sprocket- Or at least I'm pretty sure that's where it's coming from. It's not quite a grinding but it sounds like some sort of contact problem. I jacked up the bike, and the rear wheel spins freely in neutral except for a small area which seems to need just a *little* more force to spin around. Not sure if it's from the rear wheel or from whatever might be wrong up towards the front. The noise has an accompanying gritty feel, which rather reminds me of a bent rotor rubbing lightly at a certain point once per cycle on the brake pad. No amount of variation of pressure or speed in braking seems to affect the problem. There's no obvious performance issues, and I only hear it when I've got the clutch pulled in (probably because it's not loud enough to hear over the exhaust, not because it isn't happening). I ran the bike downhill in neutral and it still makes this noise. I lubed and adjusted the chain a day or so ago, and the adjustment notches are at the same point on each side. I had also ridden over a set of train rails cut deeply into the road, but I doubt that had much impact on anything. Any ideas?,Sounds like your chain may not have stretched evenly. You also may have it adjusted too tightly. You should always adjust the chain so that you have the specified slack at its tightest point. Do you know how many miles/KMs are on on this chain/sprocket set?,,,