Okay I've posted several times that I am no bicycle mechanic, so here's the proof. I have seen lots of good advice given here and hoping that someone can tell me what the problem might be.

My wife was given a Schwinn Suburban by a friend it is a fairly recent hybrid with a 7 speed cassette and 3 speed crank. Black plastic Sram ESP 7 speed derailleur and grip shifters. She threw the chain yesterday, it lodged between the smallest rear cog and the dropout.

I read up on derailleur adjustment, watched a couple of videos last night and walked out to the garage this morning fully confident that I was about to straighten out the shifting problems that that the lady who gave her the bike mentioned.

So I shifted to the smallest cog on the back and the largest cog on the front, removed the cable from the derailleur and adjusted the "H" limit. I loosened until the chain was threatening to jump off and then tightened until silent. I then pulled the slack out of the cable and reattached it to the RD. I then shifted the chain onto the second smallest cog and adjusted cable tension until it shifted back down to the smallest cog, then tightened the cable tension until it shifted back to the second cog and ran quietly. I then adjusted the "L" limit screw until the chain jumped off the largest cog, put it back on and adjusted until it was quiet and stayed on the largest cog. The "B" angle screw adjustment seemed fine with about 1/4" gap between the pulley and the largest cog.

When shifting up or down through the gears it always skips either 4th or 3rd gear and jumps right on up to the next gear. I only get 6 clicks of the shifter between the smallest and largest cog and the shifter seems to be prevented from going into the detent marked "1" through the cable by the "L" limit screw. It seems like the "span" is off but I have found no reference to a way of adjusting this.

I have adjusted the limits and indexing several different times, using several different variations of what is basically the same procedure that I found on the internet.

It seems like either the shifter is pulling too much cable for each detent, or the derailleur's range of movement has somehow become non-linear.

Sorry for the long post but I was hoping that someone out there could see exactly what I was doing wrong if I described the procedure that I went through and the results that I got.

Whether I eyeballed the adjustment or adjusted the cable tension until the chain shifted the results were the same. Skipping 3rd or 4th gear and only indicating 6 gears on the shifter (1st out of the range of cable movement). The bike chain does shift onto the largest cog, but it indicates "2" on the shifter, and when it reads "7" it is accurate as the chain is on the smallest rear cog.

What should I check next?