Bicycle Mechanics - Maddening drivetrain chatter!

So I've got a 1986 Lotus Classique with 6 speed friction Shimano 600ex derailleurs, freewheel, and I'm guessing original chain since it says "UG" on it. When I'm riding in the middle gears, especially on the large chainring, there's an incessant chatter that seems to be comeing from the freewheel/rear derailleur area no matter how much I tweak the shifters. Now I've looked everything over several times and cant find any reason for the noise. Derailleur pulleys seem good, Only thing I can think of is to replace the chain and freewheel... Any thoughts?...

Go to Sheldonbrown.com, follow procedure to check chain wear. If chain is worn much at all you will need to replace freewheel as well.

Could also be the cable-tension is too tight and the chain is rubbing the side of the next gear up. Find the cable-tension barrel-adjuster at the rear-derailleur and turn it in 1 full turns (4 quarter-clicks) to loosen cable-tension.

Could also be the cable-tension is too tight and the chain is rubbing the side of the next gear up. Find the cable-tension barrel-adjuster at the rear-derailleur and turn it in 1 full turns (4 quarter-clicks) to loosen cable-tension.

If you're using friction as indicated in the OP, than this doesn't apply, since you move the lever to center the RD by sound and feel anyway.

I wish I could hear it, because the clatter of poor trim is very different than the loud whirring or buzzing of a worn chain. Usually if you have the clatter of poor trim and it won't go away as you trim better, that's an indicator of a bent hanger/misaligned derailleur.

The other thing is could be, especially if it happens in all gears is a worn or damaged pulley. With wear, the pulley diameter shrinks so the chain doesn't index properly to the teeth on the pulleys, and there's a constant sliding or shifting as the chain goes by.

Before you spend even a dime on parts, try cutting a paper towel into strips 1/2" wide by 4-5" long. Carefully feed one between the chain and each pulley so it winds around the pulley 1 turn and overlaps itself so it can't unwind. Go for a short ride and see if it's quieter. If so, you need new pulleys (sorry the paper towel doesn't last forever)

FBinNY- Another good diagnostic tool you've mentioned. Softening up the chain/pulley interface with papre towels. Like placing bits of plastic (credit cards work REALLY well) between spoke crosings to see if the spokes crossings' indents are causing clicks when the wheel is flexing. Andy.

Thanks, FBinNY I'll definitely try that. I had thought that it could be the pulleys.

Edit: New Pulleys it is! Thanks, FBinNY.

Hate to dig up a dead thread, but I just replaced the pulleys and it seems to have just introduced a new noise... The constant chatter has yielded to a less frequent, deeper "clunk" but really only in the 4th and 5th sprockets. Is there a break in period for the pulleys? or have I just unfortunately discovered that I do indeed need a new freewheel?...