Why would your 1999 Harley Sportster 883 lose all power?

I had a similar problem with my 1200 xl and it turned out to be an air leak in the intake manifold that connects the two cylinder heads to the carburetor. But before you get into that always check the easy stuff first -Spark plugs, electrical systems and the quality of gas. One way to check it is to use aerosol engine starter fluid, with the engine running spray a very short burst around the intake manifold, if the engine speeds up that is your problem. (CAUTION -THIS IS A HIGHLY FLAMMABLE PRODUCT AND GREAT CARE SHOULD BE TAKEN WHEN USING THIS PRODUCT AROUND SPARKS, HEAT, AND OPEN FLAMES AND SHOULD ONLY BE USED OUTDOORS.) Check for any cracks in the manifold if there are none and you are confident in wrenching, re-seat and tighten the manifold connections, otherwise take it to a motorcycle mechanic. Good Luck!