I've messed with the limit screw on the rear derailleur as it over shifted and lost the chain, at first.

I've also been messing with the front gear shift cable, as shortly after I bought the bike, I found that derailleur adjusted so loose I had to take up slack in the cable. Shortly, after that, the cable itself broke, right at the connection to the derailleur, leaving the system temporarily adjusted, but leaving me relatively unable to adjust tightness at that point again. I can only adjust at the shifter. Yeah, I think I ought to just give that one up and buy a new cable.

As to other adjustments, I'm aware of how the high low adjustments work on both derailleurs, but on the rear there is a third screw which seems to adjust how far the mechanism extends. What I've found online seems to indicate this adjusts/calibrates somehow with the largest cog...not the smallest. I'll adjust it a bit one way and see what happens...as I said, I'm not sure what it does, but I can always adjust it back...and this action might alleviate the problem


any other advice would be helpful...and I'm very careful on such blind adjustments as I'm very aware of the dangers of a little knowledge....