Wow such an old thread, but my ride makes a clicking noise while backing in gear and with the clutch in. It does not make the noise while backing up in neutral. I replaced the belt, sprockets, back tire, inner chain cover bearing, and set it up on my table with both 5 lb and 10 lb belt tension. I re adjusted my belt alignment to track in and out wondering if it was some sort of belt play. I'm thinking about pulling my clutch pack to see if there is anything going on in there. Still running the bike like I stole her. 2008 FXDC with 80K on the clock

 

I had the same thing happen after I installed the stainless steel lower deflector in place of the factory plastic deflector. The deflector straddled between the two arm struts on a Softail which keep mud and water from deflecting up on the backside of the oil tank area. Anyway as said the belt moves over on the forward sprocket when you walk it in reverse and the belt comes in contact with the guard. I ended up moving the guard to the right side while doing a tire change to create the clearance needed. If you have one of the factory plastic guards perhaps it can be notched were the belt is contacting the guard.

 

Old Belt