Chainsaw Repair

Thanks Killians,
Yes piston & cylinder are trashed, flywheel and coil are ok, was just wondering why they to be replaced because of the new cylinder? Does the new piston have to go in a certain way, in other words does it matter which side of the piston faces the exhaust port?
Was a favorite saw of mine, took good care of it till I loaned it to my father pretty sure he put regular gas in it when he gave it back had no compression.
This is becoming a costly restore.
Thank you for all your help I really appreciate it.
Bob