I have been battling trees with a chainsaw for three years. I have a Sir John Red 2240. At 40 cc it's a little underpowered but it is a trooper. The first two years I kept the chain at a moderate tension no problems. This year I have already thrown three chains. What do you think gives.
The saw came with a low kickback chain. This time I want to get a pro chain. Can I use the same bar. What is a narrow kerf.
I appreciate all responses. The chains are making a dent in my beer money.
The Jonsered (that's my guess at translating Sir John Red) 2240 shouldn't be throwing chains like that. I'm ASSuming (dangerous, I know!) that you've got the CS2240, not the CS2240S. The "S" model has a toolless chain tensioner (a tensioner "wheel" on the right side of the saw). The standard CS2240 uses a right side tensioning screw like many other chainsaws.
If you're replacing chains each time they are "thrown", that means you're starting with brand new chains each time. Ummm...why? Are the chains damaged, or could the chain be mounted back on the bar?
New chains stretch significantly during their initial use. If you don't pick up on this, and your chain is sagging off the bar, there's a greater chance of it being thrown. During the first use of a new chain, you'll need to check/adjust chain tension more than when the chain is broken in. This is covered in the owner's manual.
If your saw's oil pump isn't putting oil on the chain/bar during use, your chain will overheat & stretch more than usual (leaving you prone to the chain being thrown). With the chain installed and the saw running, CAREFULLY point the nose of the bar about an inch from a dry surface. See if you can see any oil being thrown from the chain onto the dry surface. If not, you've got problems (bad oil pump, plugged oil line pickup filter, plugged oiling holes in the bar,...).
When you mount the chain onto the bar, I hope that you loosen the bar nuts slightly before adjusting chain tension. Once the chain is tight, then grunt down the bar nuts.
If your chain is dull (possibly from a split-second contact with the dirt as you zip through a log), it will heat up more than a sharp chain, loosening it, making it prone to being thrown.
The standard CS2240 runs a 0.325" pitch, 0.050 or 0.058" gauge chain. If your current setup uses a narrow kerf, it's probably 0.050". There should be non-safety chains available to fit, keeping the current bar. Bailey's has a nice saw chain selector program on its home page.
Since your saw keeps throwing chains, I hope you're using it with chaps & chainsaw gloves. Even if it wasn't throwing chains, those are cheap insurance.
Good luck!