Just changed the belt on my Zforce 500 (2019) and noticed that when I start the engine and it is at idle, the belt does not move.  If I give it a little gas the clutch engages and the belt moves but if I ease up on the gas and let the engine idle again.  The clutch does not go back to its original position and the belt continues to rotate.  Is this an issue with the clutch or is my engine idling too fast.

[2015 Z Force 800 53/Trail EPS]

On the ones with no wet clutch, like yours, the primary has a spring that helps push the sheaves back apart. If the flyweights are binding..or the RPM is high enough to hold those flyweights out a little, then you have...what you have. I would check that all the flyweights are in correctly and all tracks are clean...and that the spring is in correctly and that the idle is set correctly.