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  • Sounds unlikely: The question states that the derailleur moves to the largest cog without problems. It just moves back when pressure on the lever is released. It would not be able to move there if the limit scew prevented it, would it? Commented Jun 22, 2023 at 9:10
  • @Burki moving just enough for the shift ramps on the big cog to pick up the chain, but not enough for it to stably sit on the cog, is certainly possible with a limit screw that's not quite right. I'm more used to seeing it try to engage but drop off within half a turn, in that case, then try to pick up again, and so on, but I've seen other similar versions of this failure mode Commented Jun 22, 2023 at 10:39
  • @Chris H is exactly correct. A mm makes a huge difference. Consider the fine threads of a barrel adjuster--a full turn either way moves the inner cable less than a mm and that can make all the difference in the quality of a shift. Now consider the advice to turn out the L-limit screw an 1/8th of a turn. Close observation will detect the resulting incremental movement of the jockey wheel that can make all the difference here. Commented Jun 22, 2023 at 23:57
  • Similarly, the additional force on the lever against the last detent will increase tension on the cable forcing a hard stop against the limit screw. There's enough flex in the system to cause a very incremental movement of the derailleur cage with it's jockey wheel that the chain can run sustained on the large cog. This quality is also why a forced over shift is a good check that the limit screw is not too far out that it will allow the chain to drop off the cog into the spokes: accounts for this wee bit of movement caused by increased cable tension when stopped at the limit screw Commented Jun 23, 2023 at 0:10