I've got an NSR150 engine I'm rebuilding for the bike, it's actually a project bike and I am an enthusiast so I'm really keen, I just want to know and make sure that the barrel(although came out with nikasil plating stock) is sleeved and also if it's damaged too badly and what I should do..
It was played before I know that, and with nikasil because that's how they were produced, but I've had a look and I strongly feel that this barrel has been sleeved with cast, it had minor scors which I'll show you. (Magnet does stick to barrel inside, pretty strong magnet though)

I've measure and seeks like the piston and they barrel are both just under 59.00mm, so if I bore where do I get a larger piston or is the standard size 59.00mm?

Also, I have no idea how it happened, but when I first pulled this stop end apart, the piston had a piece broken off as if I told hit it's own conrod(that area) and then a small piece like chipped out in that section between the piston rings, which fell out once I removed the rings.