Clunking noise in gear box

Behind my starter I am getting a clunking noise, that usually happens while idling. There is a metal sounding noise followed by a reduction in rpm, then back to normal. then will repeat itself again, and continue to do so until the bike is underway. Sometimes this will not happen when the clutch is engaged while I am stopped, but not always. The sound is definitely back of the starter, the bolts on the starter clutch have been replaced already. Thanks in advance for any ideas. BIGD

My guesses would be-

1- Starter clutch malfunction.

2- A loose part or parts swimming around in the clutch (tranny version) area. Something like a pressure plate bolt and spring, perhaps.

Is it a stock or modded bike?