Three cheers to that! A possibility is that your rear tyre may be touching the belt cover? I use Avon Venoms, which are a little wider than Dunlops, and when properly aligned the rear tyre just kisses the guard.

Both my old XB9R and current XB12R squeak when wheeling them around. A loud pipe is the best cure!

 

I have to adjust mine about 2" cold, then it's to specs when warm (usually 5 miles or less) A loose belt will squeak on softails - from experience. They will also squeak if they rub the pulley on the side.

They're made with Kevlar and nothing need be done but spray/wash when you clean the rear tire/wheel for piece of mind. And as mentioned before, they are tough.