I have a Schwinn World Voyageur. I've been riding it for a couple years and like it very much. I have been planning to make some upgrades to the drivetrain and then have it repainted, and keep it as my "retro-modern" sport touring bike for centuries/brevets. I've priced out parts and services and I think I'd be hard pressed to find a new steel road bike that's a better fit for me personally for less money than what I plan to put into this bike.

The issue is, it has been making a godawful noise for about the past year. I've been trying to determine the source of the noise before I put any money into rebuilding it and so far I have been stymied.

The noise is like this: It is timed very precisely with the crank rotation. When I'm spinning lightly, it manifests as a single tick that I feel in the left pedal as my left foot comes over the top in the crank rotation. As I increase force on the pedals, additional ticks/cracking noises become audible and they get louder. The noise is present whether I am seated or climbing out of the saddle. At it's worst I feel 4 or 5 distinct cracks. It's very rhythmic. They always happen in the same sequence and always from around 2 o'clock to 10 o'clock in the crank rotation. The only time I've noticed that the noise goes away is during a spell of wet weather.

Since the noise started I've gone through three sets of pedals, the original platforms that came on the bike, then a new set of platforms with toe clips and straps, then a set of SPD clipless. I repacked the BB using new bearings. I disassembled the crankset, cleaned the chainrings, cleaned and lubed the stack bolts and nuts and reassembled. Cleaned and lubed the spindle ends. None of these things had any effect on the noise whatsoever.

I took it to my LBS last week to get a more experienced opinion. At the shop he has inspected thoroughly for things like chain rub, stray shifter cables, other things that might be striking the crank or chainrings. He adjusted both hub bearings. He took apart the headset inspected and adjusted it. He adjusted the BB (said I had it a little too tight). He swapped in a different freewheel. He swapped in a sealed cartridge BB. He inspected the frame for cracks. He says that he too, has no idea what's making the noise, and that he can't spend any more time looking.

There's one more thing that it has occurred to me to try that I don't think he did. I have a second crankset at home that I think I'll swap in when I get the bike back. Perhaps there's a crack in the spider or a crank arm that has gone unnoticed. I guess it's also possible that there's a crack in the frame or a failing braze joint that we weren't able to find.

I really hate to have to give up on this. If I do then I'm left shopping for a new bike (not happy with the upfront cost and lack of tinkering involved if I go that route) or shopping for another old bike and starting from square one (trading a bike of uncertain condition for a second bike of uncertain condition).

I'm hoping someone might have either a) some ideas for things to check that I and my bike mechanic may have overlooked or b) some way I can test to know for sure. Any insight is welcome!