Piston rings

I would if you're doing this type of maint. Ring's aren't hard to do.

Rotax states pistons can be reused if they measure within the 50% or under total wear.  (see heavy maintenance manual)  At 2000 hour however the rings should be changed.  If you are not going to overhaul as per the Rotax requirements then you can always just take that responsibility and evaluation yourself.  

If you do reuse rings they have to be kept on the same pistons and assembled back into the same cylinder.  

Cheers

Thank you, I know but the owner find it very expensive 

If it will not stand it's easy to install new rings later