Chainsaw Repair

Yep.  It's old.  But it's my trusty friend that has always performed well.  After being in storage for 5 years, now when the sparkplug is out, it spins over just fine.  With the plug in, I can get it to turn over once and the compression feels normal, but after that one rotation, it seems to back up against a ton of compression. Someone else posted this problem with a different model Stihl saw and got replies mentioning a possible faulty starter mechanism.  That doesn't sound right since the starter pulls as it's supposed to with the sparkplug out.  It's a compression issue since I can feel it backing up against impossible compression with the plug in.

Any ideas?