Assuming you purchased your 883 new, you paid somewhere between $7,000 and $8,000 for your ride. Money well spent in my eyes, but unfortunately, HD only used about $10.00 of that purchase price to provide you with a suspension. In short, your bike looks like it has a real suspension, but that's where it ends.
Hobbit is 100% correct (again). I replaced my suspension with Progressive Suspension components and never looked back. My Nightster suspension now has controlled dampening and rebound, not to mention that I got the all black shocks and the looks are great. Up front, I replaced the fork springs again with progressive units and the results were great! Takes a little coin, but well worth the changes! I can now ride my Nightster tank to tank and can still walk afterwards! (My weight nearly the same as yours).