I converted my primary to belt ten years ago.
I flat love it!
The primary runs DRY, so no leaks, and blessedly DRY clutch plates, truly no maintenance.
The belt is much lighter than a triplex chain so the primary feels smoother and lighter, and I feel the gearbox shifts lighter.
I would not go back to a chain primary.
Yes it is a pricey conversion, and you do have to purchases or make up a left side threaded gearbox adjuster to ensure the belt runs true.
I have two pictures of my left side threaded adjuster in the FILES sections of the INOA online Norton forum to view.
I remove all three primary cover inspection covers to vent the primary, other don't and say no necessary.
The belt baskets and the engine plates get hot and expand so the belt is set up with significant slack when cold.
Hope this all helps!
highdesert