I have a 1990 Sporty 883c,
I've noticed that over time the rate of acceleration was decreasing, and now when I engage the throttle (regardless of gear) I feel the slightest hint of power being sent to accelerate, yet I do not.

Essentially the engine revs but no power is being engaged, any idea what the issue is before I call it quits and hit a shop?

 

Sounds like the clutch is slipping big time. Is the cable binding up or really out of adjustment. Have you tried lubing up the clutch cable?

 

So, the engine revs alright when it is in gear yet the bike doesn't move or barely moves when you let out the clutch? Posibly the clutch needs adjusted, cable is mis-adjusted, clutch needs replaced, or you have a bad throwout bearing. There are a many threads on these issues.

 

Clutch needs work.