Almost all chainsaw cylinders are plated and can't be overbored. Probably the cost to fix the saw will excede the cost of a new similar saw. That is what is called a clamshell saw. The cylinder is part of the crankcase. You must pretty much disassemble the entire saw to change the cylinder. By the time you buy a cylinder, piston, bearings and seals you could buy the saw new.
I bit the bullet and took on the 2010 Homelite UT10519 46cc full rebuild. The new stuff for $120-$150 in box stores is disposable and less quality than the older stuff I have found. It cost me $80 in parts (cylinder, piston, piston ring, ignition coil, spark plug, broken muffler bolt and a missing screw. Was fun doing the full rebuild and this saw is still basically brand new (came with case & original packaging).
Piston and cylinder was shot and the heat probably fried and cracked the coil and spark plug (ohm readings out of spec).
While apart I replaced the brittle fuel lines/filter and took apart & cleaned the ZAMA carb. Carb was in good shape. Got it all put together again and it fired right up. Was running, but way out of tune. The guy whole sold me the saw for $10 said he was playing with the jets, so I seated and then backed off 3 turns, fine tuned, sharpened chain and she's humming.