Without hearing it for myself, all I can offer is some possibilities. The first would be a lifter or lifters that bleed down overnight and are slow to pump up the next time the engine is started. That's been an all-to-common problem with Harley lifters over the past half dozen years or so, and Harley will call it "normal" even though it isn't normal or acceptable. Another possibility is piston slap, which is worse with a completely cold engine and improves as the pistons heat up. And of course the same thing can happen with other parts of the valve train, such as rockers. Harley's have a multitude of areas subject to sloppy fits that create noises. If you ever get a truly quiet Twin Cam engine, you need to pull in the clutch and restart it because it's obviously not running.
Jerry