Hi everyone. I just bought a bike and it needs a little work. It was a good deal tho so its ok

When I roll on the throttle and realease it, it doesn't snap back to the off position, it kind of slides slowly back, so that when I'm shifting it I have to push it back. I tried opening the box, lubing it, and that did not help, so I followed the cables to where they attach on the other end....keep in mind I know little about bikes, and I found that spring thing that the two cables ends are connected too. The one that is higher up, appears to be loose, so when I let off the throttle it has a little slack before it tightens up. Now I figured that I must need to tighten the nuts. I can't get a wrench in there without taking off the tank. So I removed the seat and unscrewed the bolt holding down the tank and lifted up. The tank is still attached somewhere I think. I have no manual so I'm not positive where to go from here. Any help would be GREATLY appreciated. Thanks! Holly