80's bike, Araya A20 rims running different sets of 700 x 25..

Weird noise, sort of like spokes resetting, but much quieter. I checked the spokes, repacked the front hub, switched to a different tube/tire combo, but there remains this light tinkling sound coming from the front of the bike. I repacked the headset a few years ago, but that's all that's left that I can think of trying. Under weight only, not speed dependent, no particular cadence...just random.

I speculated it might be new tires throwing up tiny debris into the frame, but it was just the same with well used different slick tires, and change in speed or surface doesn't matter.

I road the bike hard on the flats a few weeks ago, handled everything just fine but all of a sudden it starts makes this odd tinkling noise.

Anyone solve a similar mystery sound? As I write this I am wondering if I have a fissure crack in the rim somewhere....