Do a stage 1 and throw a cam in. You'll be much happier with the sound and the ride.

 

I had assumed it was the tranny, but it could well be from the valve train now that you mention it.
I'll see if I can identify the source better.

 

Go back about 1000 Meters, give her all she's got, and ride it right into that lake behind you.That'll fix it for sure.

 

Then I'd just get Clachety blubly Clatchety blubly.....

 

I didn't catch what year your ride was, but your title was clackity clackity, that sound is usually more evident in the compensator, I had that too, which is one of the reasons why I dumped the stock one to a screamin eagle compensator.
Now if your talking about sewing machine noise, that's a little different, and I am pretty sure that is coming from your valve train, or in another words, the engine. Different oil, will help, but think it's just the design friend, don't believe its anything detrimental but pretty much like someone said above, do a stage one to it and you'll hear a little more of the intake and the exhaust breathing, than a sewing machine, plus it'll run a ton better anyway.
If none of that sounds good to ya, then slam an ipod on, crank it up and roll.

 

Some are a lot louder than others. My brothers "B" motor in his fat boy is quiet. My "A" motor in the glide is loud as hell. I read a bunch of posts on here about Synthetic oil added to the sewing machine noise so I tried going back to conventional oil. It didn't eliminate it but it did improve it a great deal.

 

+1 on the Mystik JT8 ive been running the 15w50. Mystik has been around forever and if you check it has everybit the additive package as Harley 360 and @2.29qt.

 

Plus 1 on the Lucas Oil stabilizer. I run 4 ounces in the tranny mixture and about double that in the oil tank when I change the oil. Seemed to help my Evo.

 

I believe the clackety clackety noise I get is from the primary (chain tensioner?).
At this point,I don't have a tach on the FXDBI, and I do tend to keep it wound up, but it happens whenever I get down near the low part of the rev range in any given gear. I'm not talking about lugging it. I'm talking about any RPM except wound up. It was that way when it was stock, and it's that way now, with Big Sucker, Thunderheader, and 37h cams. I think some aftermarket guru needs to come up with a quiet(er) fix for it.

 

Install some sound absorbing Dynamat batting sheets in your rocker covers ...