Hi

I recently changed my freewheel (from 5 speed to 6 speed), new chain, new cables but now it slips through the gears whilst I am riding on it's own accord - any advice?
I tightened the downtube shifter and this helped but hasn't totally sorted it.

Gears - Campagnolo Nuovo Record circa 1970…


Cheers
Mark

What freewheel? If Suntour, is it an Ultra 6 spaced freewheel? If so, you will need a narrower chain, as these used 5mm spacing instead of the 5.5mm used for standard 5 and 6 speed freewheels. What chain did you use?

Is the wheel in the dropouts straight? Derailleur and hanger not bent?

The chain slips between the cogs? Is the chain too narrow for a traditional-space freewheel?

I think you are on the right track here. In my experience, the shifter is usually the culprit in these cases. Especially with the older Capagnolo record shifters. The last time I experienced this problem, I disassembled the shifter and cleaned all the washers and innards with WD40, re-assembled, tightened again, and the problem was solved.

Good luck.

I think so too, Gaucho, and, fwiw, I only put a very light coat of grease on the sliding parts inside, then wipe them almost dry before reassembly.

^ Same thing I do to them... thin film of grease after thorough cleaning.

Not clear from the OP's post whether the chain is skipping, I would find it difficult to believe that it would be dropping between the cogs. 11 speed chain, maybe...

If it actually slips down through the gears, the lever movement will be noticeable. Such a cases are almost always the shift lever.

Chains that are too wide will not nestle down properly in the cogs and will usually hunt between one or two cogs and may slip down one gear but typically not slip through all the gears.

I agree with the shifter theory. Also, check that your cable is just barely under tension with the shifter in the forward position.

Tighten shifter + cable tension. One or both of these has always solved this for me.

Sorry - it's not actually dropping between the cogs - it just gradually changes gear itself until it's on the smallest cog - especially when i'm going up the big hill on my commute...

It is a Suntour but not sure if it is an Ultra 6 - it was my LBS that fitted it - they did tell me they needed to fit a new chain - I would have thought they got the right one as he is a vintage bike specialist...

I emailed my LBS and he suggested this might be needed - also he said weirdly the shifters were put on back to front so he turned them round when installing the cables...

After I tightened the shifter the problem wasn't so obvious but before it changed gear itself really quickly, with the shifter moving itself - maybe there is mileage in your suggestion of cable tension - could it be too tight, so it is forcing the gear change?

Don't think so. The only thing keeping the derailleur up on the big cogs is tension from a properly adjusted shift lever bolt, with the return spring in the derailleur body wanting to bring it down to the small cog and its stop. So it's a question of balance between the two.
I'd disassemble the shift levers and clean them off. Also make sure all the parts in the levers are in the correct position and all there.
If he is a vintage bike specialist it's unlikely he got it wrong, or left too much lube on the parts, but it's possible.

Huh? Is that even possible? Did your bike shift properly before he worked on it? Are these banded shifters or does your frame have braze-on fittings?

It's possible I suppose that the various washers and innards were assembled incorrectly.

Old campy friction shifters make nifty key-ring ornaments but they just suck as far as actual shifters. Usual fix back in the day was to replace them with either simplex or suntour micro-ratchet downtube shifters wich actually function much, much better than friction only campy shifters.

OK, I'll admit that this is at least partly true, but they do make awfully nice downtube ornaments as well.

And actually, with that thin coat of grease mentioned earlier, and the tension set just right, I find them quite likable.