Hi, this is my first time posting here and I'm not very bike-literate. I have a problem with slipping out of lowest gears and I think it's a problem with the rear derailleur spring having too great a tension. The derailleur throws the chain correctly in both directions so I the problem isn't related to those simple adjustments. But once I've shifted to lowest gear, the derailleur springs back a little, pulling the chain to the 2nd or 3rd largest cogs and would only remain on the largest were I to hold down on the shifter, fighting the spring as it were. Can I fix this or, looking at the attached photos (not allowed to post photos yet) could the problem lie elsewhere? Many thanks for any advice. Bruno

To confirm, the problem is not holding position to keep the chain in the larger cogs in back.

the most probable issue is at the shift lever.
not holding tension. As it is a Spidel rear mech a decent chance it has retro friction shift levers
if so, internal parts can wear or fracture- this would be the easy to assess and expensive to repair- no parts any more- one would have to buy an assembly. Regular friction levers would work too and be cheaper.

If it is the shifter slipping, I've heard replacing the flat-head screw on the lever with an allen will let you get it tighter and a few more miles out of it.

This is sometimes true even when the shifter is fine internally, as the barrel inside of the lever may be rotating (when it should be held stationary by the bolt's tension).

I would oil up the inside of the lever and tighten the bolt.

Please read ALL of my posts in this thread (verktyg):

Simplex SLJ 6600 real life capacity

WHATEVER YOU DO - DON'T... Don't touch these hex sockets with the plastic plugs in the PIVOT BOLT! They're for adjusting the tension during assembly not for mounting and removal of the derailleur !!!!!




BTW, I have some Nylon plugs to fit in these sockets... FREE - PM me




For Retrofriction levers, there's a lot of info in this Flickr album I put together about 10 years ago. Click on the photos and read descriptions below them :

https://www.flickr.com/photos/282672...57627163433202

Good luck...

verktyg

Tightening or loosening the pivot screws on a Simplex/Spidel/Mavic retrofriction shifter does not change its resistance against the derailleur return spring(s).
All resistance on the Retrofriction system comes from the spring clutch inside the shifter body that grips around an internal shifter pivot hub, only in one direction. Think of it as a sort of one way ratchet mechanism, without the detents or clicks.
A truly elegant and surprisingly simple piece of bike engineering, from, of all people, the French, who had their big share of bicycle component questionsble designs, back in the day.....