Overall Rating: 4.0 (of 5)
I think about this riff as being made up of 2 very similar parts. The first of which being 14 beats long, and the other being the same with 1 note left out...bringing it down to 13 beats long.
The first part is 3/4 timing until the last bar in which I remove an open note
The second part is 3/4 timing until the last 2 bars which have open notes removed.
Since 3 notes have been removed from what would otherwise have been a completely 3/4 riff, it will match up with the rhythm behind it if both parts are played together.