045 Compression numbers

[Kenskip1]

OK,so a family member was cleaning out a neighbors garage. He found a 045 Stihl that had been setting for many years. The owner had passed on. Anyway he made an off that was accepted. So, it has great spark and 155 pounds of compression cold.He replaced the gas line and it started right up.So after running it for a bit and it was oiling, he rechecked the compression. Hot it was 125 pounds.It starts and idles fine but the lower numbers have my brother a little shaky. Any suggestions?Is this within acceptable tolerances? Thanks Ken

 

[hotshot]

That’s a great old firewood saw!

All saws will drop a bit when warmed up, but not that much. I’d expect about a 5% drop, or 7 psi lower if he gets the average well used S045‘s reading of 140# cold.

Compression is at the lower end, but it still should cut fine being an 80cc saw with a 52mm piston. If it’s an early 045, it will have a smaller 50mm bore with a 1mm thin top ring.

I doubt it dropped 40 psig when warmed up, rather he had excess oil in the chamber on the initial cold check.

See what the compression reading is now after it cools down, then pull the muffler and check the spark screen for blockage or any carbon scoring on the piston face.