If you read previous posts you will find the answer.
So, the
biggest problem with the open drivetrain is not dust.
The biggest problem are small stones etc that damage the drive belt and pulleys.
One thing that can happen is that the stone gets stuck and locks the drivetrain. The result will be a damaged belt and the pulley will look like this:
The second thing than can happen is that the stone gets stuck between the belt/pulley and the rear suspension mount. This will wear out the belt
very quickly and it snaps off.
One of these things will happen sooner or later if you run on a track/surface with small stones.
I made this diff/pulley protection for my own needs. It solved my problem and has now also solved a lot of other 511/501X drivers problem.
I havenīt had a single problem with the drive train this summer. In fact, Iīve used the same belt and pulleys all season, racing on tracks with small stones.
But whether you think you need the cover or not is up to you to decide.