Just stating what a local rep told me in person.
I personally had four 5100's when they first came out, two of them wouldn't run at all, bad coils. The other two were sucking air, no carb sealing rings. I also had one that wouldn't idle down after making long cuts, an overheating issue. At the Ohio gtg last month our host had a 5100 sitting out with the clutch and oil pump removed, the bearing was spinning in the case with zero resistance, the bearing itself was fine.
Look I know a few people really like these saws, but they had or have major design issues. I've literally seen in person more of them not running than running. On top of all that Dolmar seemed to make up excuses to get out of warrantying these things, it hurt Dolmar big time. The three dealers In my area dropped Dolmer because of the 5100 + slow sales.
I forgot to mention the intake boot spring clamps would slip off as well, causing an air leak.