Picked my newly built up road bike from the shop this am, they couldn't quite get the rear mech shifter (7 speed dura ace downtube shifter) to work. shifting was fine, but it wouldn't stay in some of the gears, the lever was returning slightly to its original position. Suggestion was that the lever was either broken or not very good (Ebay special, so quite possible). So… I re-fitted the original plastic Sachs lever, which, though ugly, worked fine prior to rebuild. Now it doesn't work at all! It shifts fine, and all the indexing matches up, it just won't stay in gear, every time i let go of the lever it returns to its original position (which is a little annoying!). Any suggestions? I wondered if maybe the spring in the rear mech was too much? (its an 8 speed dura ace rear mech). What am I doing wrong? How do I fix this? I really want to ride my new toy!

is there a bolt, d ring or something else on the end of the shifter. It sounds like it might need to be a bit tighter.

is it a case of tighten until you can tighten no more, and then give it some more?

DO you have a friction mode on them? If so does that work fine?

Seems not on the old Sachs ones… probably on the dura ace?

As mrmo, there will be something to tighten on the outside of the shifter. This needs to be slightly tighter than it currently is.

put the dura ace back on, now holding all gears except the top ring… time to man up on the hills me thinks!

Is it a new rear mech? Perhaps the return spring in the mech is too strong. An older mech with a worn spring might actually work better!

new ish,,, i wondered that? most gears no work so we'll see how it gets on