I've got a Klien Pulse Comp that is about 6 years old. Back in the day it was a pretty good bike. I'm looking to just tune it up and ride a mix of street and trails. It's got a flat tire (slow leak) right now and probably could use new rubber. I figure I'll get some new tires and tubes and clean and lube everything. Another thing I noticed it that it does not shift right. I can not shift into certain gears. I'm sure it just needs some adjustment but I can't figure out what. I've tried to tighten the cable but it didn't work. Can anybody give a newbie some tips?