My motorcycle makes a single kind of loud click?!?

I have a 2001 Suzuki gs500. I've done all routine maintenance after i bought the bike. It still runs fine, BUT at about 900 to 1100 RPM when I move the throttle just a LITTLE bit it will make a loud single click noise. Not super loud but enough to make me ask this question. I don't know much about motorcycles it doesn't make this noise at a high rpm or at regular speeds or even all the time.. I've read maybe something about the valves needing adjusting. Also, I know for a fact it's coming from my engine and not my muffler.