EC 250 top rebuild question

[julianorettore]

Good Morning
I am making the top end rebuild of my gas gas 250, year 2008, I verified that the motorcycle has a wossner 8052DB piston, measure B, in which when measuring the piston I found that the lower diameter is larger than the diameter n top, measuring 66, 39 and 66.29 higher. Is that correct?
I noticed that there is a rebound in the cylinder at the top, where there is the end of the course of the rings, I believe the cylinder will have to be repaired. When I get home I will add photos so that you can help me more precisely
(translate portuguese > english by google)