Short answer: Pull up on the chain with gentle pressure: you should be able to see about three drive links (the bottom part of the chain). Too tight wears out the end of the bar. Too loose and the chain wears unevenly, and if it keeps coming off, it's probably too loose. Check the clutch cover nuts and make sure the tensioner is working.
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What Phil says
"I normally like to have 3 drive links. You should be able to see 3 drive links with gentle pressure pulling up on the chain. If you don't know what drive links are, it's the bottom of the chain. Don't have it too tight, or you're going to wear the end of the bar out, and too loose, you'll see it wearing in different spots as well. If it keeps coming off, you've probably got it too loose. Check your clutch cover nuts, and check your tension is working correctly, and you should be fine."
The three drive link check
- With the saw off, lift the chain away from the bar with gentle pressure.
- Look at the drive links, the bottom of the chain that runs in the bar groove.
- You should be able to see about three of them. Adjust the tension until you can.
| Tension | What happens |
|---|---|
| Too tight | Wears out the end of the bar |
| About right | Gentle pull shows about three drive links |
| Too loose | Wears in different spots, and the chain can keep coming off |
Chain keeps coming off?
It's probably too loose. Check that the clutch cover nuts are tight and that the tensioner is working correctly, then re-tension.
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From Clogger Answers, episode 1. These are Phil's opinions, based on his professional experience. Always follow your saw's manual and wear the right protective gear.
Phil is a professional arborist based in Invercargill, New Zealand, who runs saws every day with his crew. Clogger makes chainsaw pants and chainsaw chaps.