Back gears skipping up and down

[agascho]

I recently got my biked worked on and they fixed the shifting in the back, everything was working flawlessly (which means the bike was shifting perfectly). I also got a brand new chain with the maintenance.

Last night I blew out my back tire so I replaced the tire and tube (this required removing the back tire). Now when I shift gears the chain moves up and down between the gear I was in to the gear I want to be in. Eventually it may decide to shift down (which is what I want) but other times it stays where it is.

If it doesn't move between the 2 gears it will just skip down farther than what I want it to. I have 7 gears in my back sprocket.

I have down tube shifters.

Any suggestions on what I can do to fix the problem?

[GeorgeET]

First make sure you reinstalled everything correctly. Than since it was working before your most likely cause is the cable needing readjustment. Not sure which direction you are having problems. But if its missing going from a large cog to a small one put more slack in the cable with the barrel adjuster usually located at the derailler (some bikes at the shifter too). To put more slack in turn the barrel in clockwise. Do one turn at a time and retest.
If you are having problems going from a small cog to a bigger one tighten the cable rotating the barrel counterclockwise.