I have purchased a 03 fatboy with 92K miles last year. At the end of this summer it developed an engine rattle. Not sure of the rpm but it is most noticeable at 10 mph in first gear, 20 mph in second, 30 in third gear, 40 in fourth gear and 50 in fifth gear. It doesn't really change with load just the rpm. The engine was supposedly rebuilt at 75K. It is clean, no leaks or any other noises. I have spent the last40 years on an iron head so this bike is new to me. Any ideas on where to start?

 

I'd start by looking at the lifters. They are a common failure and produce a rattle at various rpm's when failing. Remove them and pay particular attention to the rollers and bearings.

 

Check kickstand Ihad a bike where it was bouncing off the frame.

 

Shifter linkage, loose exhaust heat shields or brackets.

I think before I tore into it I would change to a good (HD?) Dino oil at 20W50 and see if it mutes the rattle. If so, It might just be "normal" top end noise. A lifter is pretty much unique in the way that it sounds. In my experience a lifter taps more that it rattles. Also might be carbon related pinging, try some SeaFoam and new plugs?

Just thoughts, as I am no expert.