I watched some videos about changing the CVT belt and it looks pretty easy if the shims are pre-done at the factory.  looking at the UtliMax belt replacement but what does everyone think.  My 2up has 2000 miles and its hard to shift into low because it grinds.  I think its time to change the belt?

https://www.amazon.com/Ultimax-Drive-Belt-211142/dp/B074XG9MC3/ref=sr_1_1?dchild=1&keywords=0180-055000-0001&qid=1607740513&sr=8-1

Hard to shift because it grinds implies the secondary is still spinning, which implies the primary isn't fully retracting at idle.

First focus should be on the primary.

[2015 Z Force 800 53/Trail EPS]

If it shifts easy when not running but hard to and grinds while running, like doug80638 says, the belt has enough contact with the primary to spin the secondary and thus the transmission. With a CFM dry-clutch system many times it's one of two reasons. The first and most often reason is that the operator allows the unit to idle for long periods which excelerates the wear of the one-way idler bearing the belt rides on while idling and seized or running dry it will make the belt spin. The second most often reason is the primary can't or isn't releasing enough to withdraw sheave contact with the belt. Usually due to some interference in the flyweight area...like packed with dust.

As a rule, belts wear thinner and stretch over time which would make belt wear less likely to be the cause of your problem..unless it's coming apart... so...apart it must come for an inspection. I'm sure the cause will present itself.     

Just like already mentioned. Mine started getting tough to shift while running. Took it apart and turns out it was fine dust packed inside. It wasn't much, but it doesn't take much. I figured it was fine dust in combination with possible steam from mud holes or crossing creeks. It's not a difficult job. The tricky part is holding the clutch all the way on while putting the nut back on. And don't forget it's reverse thread.