I was given an old Stihl 045AV that was suppose to be a good saw but had not been run in over 15 years. It started right up and ran fine. I cut a couple 8 inch logs and it seems to run fine. I took it to a local repair shop for a tune up. They said the compression was only 90 and if I put a heavy load on the saw it would over heat. I have never heard of this before. Is compression at 90 an indication the saw should be rebuilt immediately or can it still be used? Can it be used under heavy load? Any thoughts would be appreciated.