Tubeless type tyres on an XT660?
 

Looking at Metzelers website it lists the following TL marked Karoo 3's as suitable for the XT660 (mine is an R but I think they are the same rims as the Z), but the bike has a spoked wheel.

90/90 - 21 M/C 54R M&S TL
130/80 - 17 M/C 65R M&S TL

On my XT600 I only used Tubetype (TT) tyres.

Anyone fitted tubeless type tyres to their XT? Did you just fit tubes? Or did you need to seal the rims?

No problem fitting them, use a tube as if they are TT tyres :-)