I'm in the process of getting set up to start a full restoration on a BS50 Sport. The bike was thought to be a runner, although I was never able to get it started. I spent some time trying to figure out what wasn't working and I found that I was only getting an intermittent and weak spark so I just packed the bike away and bought a new coil and ignition parts that went into the storage bin for that bike. I recently pulled the cylinder off with an intent to send it out for a fresh bore to accommodate the first-over(0.25) piston I already had. The machine shop cautioned me that a first-over bore might not clean up the cylinder enough if there was existing damage. Well, as it turns out, there is some damage (see attached pictures).
What really caught my attention is that the area between cylinder bore and the transfer port opposite the exhaust seem to be real close. I put a digital caliper on it and it measures about 1.7mm at the thinnest part of the skirt. The farther you go down the skirt, toward the top of the cylinder as it's laying upside down, the thicker it gets.
Also, on the photo with the burnt and scarred piston you can see that both rings look to have a shiny appearance. It was my understanding that the iron cylinder used a chrome plated top ring and an iron bottom ring. Both rings look the same to me.
So my first concern is whether or not the cylinder is suitable for a rebore, assuming I can find a second-over (0.50) piston and rings. Secondly, is the damage to the piston and bore from someone installing the wrong rings on this piston?
Any thoughts out there from anyone with iron cylinder experience is appreciated. Thanks.