I've got '05 Sportster 883.
The problem is it has air/fuel (or mb ignition) problems under 2000 rpm. The bike responds to the throttle very slowly and has no torque under 2000 rpm. No acceleration almost. The harder I open the throttle, the more noticeable the problem. The fact is after 2000 rpm the bike pulls hard and accelerates well till 6000 rpm on any gear.
I installed 48 idle jet, 190 main jet, an adjustable needle jet (set the E-clip on the 2-nd position from top). Carb is been cleaned and the diaphragm is ok. The mixture screw is 2 turns.
Is it a carb issue or could it be a crankshaft position sensor problem? (There is no error codes found)
Thanks for the help.
P.S. the problem was on stock jets too (42/170 and stock needle)

 

Check and clean the transfer passages carb. They are the ones that the butterfly covers, uncovers at small throttle positions. If the bike has been sitting, they are likely plugged. It's probably worthwhile to do a compression check. How well does it idle? Did this problem start after sitting. What is the condition of the plugs and plug wires?