Re: have REAL power loss now!
I just finished adjusting the throttle cable on a diy bike. In mine I had to turn it a bit before it actually did anything at all. Then when I went all the way to the end of the throttle, I didn't have it wide open because the throttle had already played out taking up the slack.
If your engine responds instantly to the throttle then you are fine. It there is a some slack not in the tension but in the engine response I would tighten it. If it responds instantly then I wouldn't bother with it.
If you didn't find a leak and your throttle responds, you are past anything I know to do. Try Norman he knows everything about these engines and carbs.
by the way the pressure you feel on the throttle when the slack is out is the spring not necessarily the needle moving I think. At least that is what it was on my diy bike i worked on today.
When the needle was actually moving the engine responds. It ain't much but it's the best I can offer.
My posts have entertainment value only. A bike ain't yours till it has your blood on it. Then it owns you.