I've got a Suntour BL rear derailleur that doesn't want to stay in low gears (biggest cogs). The limit screw isn't even close to touching, but it won't shift past the 3rd biggest cog. And after it's shifted there, the derailleur "springs" back down to smaller cogs. It won't stay any lower than the 2nd largest cog. Nothing seems bent, but there is a little lateral play if I grab the bottom gear and wiggle side to side. The spring action pulls the derailleur out toward the smaller cogs and the shift lever returns all the way to the high gear setting. Friction shifters, of course, on an old Lotus. I've tried the "B-tension" adjustment and nothing changed. Thanks for any help, I tried to find other threads with similar problems but the google search makes it difficult.
I'll admit I'm new to this and I couldn't figure out what mechanism was supposed to work against the spring action of the derailleur. I didn't realize it was in the shifter!! I just tightened down the friction adustment and it works perfectly now. Thank you very much!