The last couple of times I've been riding I've noticed an odd sound coming from my bike. After I've just let out the clutch in first and second gear I get this gravelly/rumbling kinda sound coming from what sounds like the engine, maybe in front or below it. I've only noticed it happening in the lower gears (maybe because wind speed doesn't allow me to hear it in the higher gears) and only after I've let the clutch out and I'm getting up to speed. I haven't nailed down any rpm range, but I know it isn't a constant thing, only when I'm in the lower range of the gear. It has me a little worried. I bought it brand new less than a year ago and I have nearly 10K miles on it. I had maintenance done to it at 7K miles (had valves adjust, carbs synched, general maintenance). I've only noticed this on the last few times I've ridden it. Performance doesn't seem to be affected (as far as I can tell). Could it be my chain, like the front sprocket is worn or something? I've tightened my chain recently but I haven't checked if it has reached the stretch limit. I admit that I don't do as much chain maintenance as I should. Lemme know what ya'll think.