Noticed the other day that I get a hard clunk/clicking sound while riding. Sounds like it's coming from the clutch area. The clunk seems to be inline with chain rotation. Not sure if it's from a seize in a chain link, or something in the clutch.

Any tips?

you could inspect the chain... maybe?

When my ZX11 chain stretched while I was touring Europe, it make a clanking/clunking sound. I was glad that was all it was.

Yeah, they need to be changed. I have almost 28,000 on the stock chain and sprockets. Just wanted to see if there were any other possibilities.

Is there a risk of breakage?

1.Stick the back wheel in the air, spin the tire. See if that noise can be heard in the static, no engine running.
2. Start engine in neutral. Click in gear, then let the back wheel still off the ground, spin in gear, engine running.

It's either chain or clutch. Was a link installed? Depends how well the chain was staked, or quality of chain for any risk of breakage.

Hub wrote

Depends how well the chain was staked, or quality of chain for any risk of breakage.

Stock chain. Do the the stretch test measuring across 21 pins. Measure in 3 different locations. 12.7 inches is service limit.