Hearing an odd kinda quacking noise at around 2100 rpms coming from the left side while riding at low speeds (can probably only hear it at low speed due to the wind). No clue how else to describe this noise. It's generally light but goes away as soon as i pull out of those rpms. Bike only has like 700 miles on it so far so still breaking in basically.

Assuming it's the belt tension or wheel alignment. That said, i'm a bit confused about the belt tension and what's in the manual vs what reality is. The manual says this:

"Measure belt deflection as viewed through belt deflection viewing window while holding gauge steady. Each deflection graduation is approximately 1.6 mm (1/16 in)."

Those marks though on the plastic are 1/8 of an inch though and not 1/16. The manual also shows this weird pic where it looks like they are trying to say the space BETWEEN the marks is the 1/16 which would then mean each mark and a space is 3/16.

Do you take the manual literally in this case in that since belt tension is supposed to be 1/2 to 9/16 that you just shoot for between the 8th and 9th hash mark? (this really wouldn't be 1/2 inch though) or between the 4th and 5th mark which actually would be 1/2 to 9/16?

 

I like to lay a carpenter's tape on the floor and put the upper extended tape against the belt. Helps if bike is vertical on a jack or stand. Push with special tool or pull with fish scale 10# there and see how far the belt deflects. I've never used HD's slotted window. Eventually you can reach down when the belt's cold and deflect the belt by hand to test.

 

I like it at about a 1/2” with someone sitting on the bike .
No tape or measuring stick , I just do it by eye .

 

I bought the Harley belt deflection gage back when it was $11.95 (many years ago). I marked off about 2 inches in 1/8" increments on a sheet of paper, cut out this "ruler" and taped it to the side of the belt tension gage. Then I place the gage against the belt and eyeball the scale against the edge of the belt guard and count how many marks the gage moves when I reach the 10 pound mark on the plunger.

 

Like others have said, use a tape measure or ruler. I can't for the life of me count those marks. No contrast makes it a pita