Changed belt to chain. Now adjuster keeps losening on 2008 haley road glide

The primary chain is self adjusting on this model

Does it sound like a chain noise, coming from the primary case?

In 2007, Harley changed the primary chain tension adjuster to an "automatic", spring loaded one, that doesn't work very well.

You can bolt in an older manual adjuster, BUT the area that USED to be an inspection/access cover on the outer primary cover is now a solid area, so you'd have to remove the outer primary cover everytime you adjust the primary chain.

There are some aftermarket "automatic" adjusters out on the market.

Open belt drives are for one thing and, in my opinion, one thing only, looks. Personally, I wouldn't have one. They look plain dangerous to me.

The biggest problem people have with them is belt breakage. Harley came out with two models that had dual belt drives, the Surgis models and the FXDG "Disc Glide" in 1984. Both models used the same type of belt drive which was a fairly narrow belt. Owners were plagued with belt breakage problems and some even converted the bikes to chain drive like the rest of the bikes Harley made had on them.

I'm sure belt drives have improved since then but as to what the advantages of a belt drive is over a chain drive, I have no idea. Some say that it reduces maintenance, a claim that I don't buy. My vote is against it but then, It is your bike.

Losen the bar mounting nut, then losen the chain tension adjustment screw until the chain can be reinstalled, then tighten the tension screw until the chain just sags 1/8" or so at the center of the bar then retighten the bar mounting nut.

before you adjust it, belts are on tighter than chains, 1/4 inch up and down play is norm