When breaking in a new saw, it is necessary to check the chain often, because the new chain will stretch with use. The chain or bar might have suffered some damage when the chain came off, so here's what you need to do.
1. Drain the fuel from the gas tank (to avoid a leak).
2. Lay the saw on it's side so the bar is up.
3. Remove the 2 nuts holding the side plate on the saw.
4. Remove the side plate and the bar and chain.
5. Remove the chain from the bar.
6. Carefully check the slot in the bar where the chain rides... clean up any burrs with a file and make sure that the slot has not been widened at any point.
7. carefully check the INSIDE circumfrence of the chain, inspecting the dogs that ride in the slot in the bar for damage. GENTLY file any burrs off of the dogs but don.t remove any more material than you have to.
8. Reinstall the bar on the saw.
9. Oil and reinstall the chain on the bar making sure that the cutting teeth are facing in the correct direction (The cutting teeth on the top should face toward the tip of the saw).
10. Adjust the screw at the front of the side plate so that the nib threaded on the screw goes through the hole in the bar when you put the side plate on. (This is the chain tensioner). When you are sure that the side plate is on and the chain tensioner nib is protruding through the hole in the bar, snug the two nuts on the studs protruding through the side plate (do not tighten them at this point).
11. Make sure that the two nuts are not too tight, as now you are going to adjust the chain tension. Tighten the chain tensioner screw (at the front of the side cover) until you can pull up on the chain at the center of the bar
and the chain pulls up 1/16 of an inch... no more. The dogs should not come fully out of the slot in the bar when you pull up on the chain. Adjust the tensioner until those parameters are met. Now tighten the two nuts on the studs sticking through the side plate... 170 - 200 inch pounds should do it... don't strip the studs.
12. remove the spark plug wire from the spark plug, and try to manually run the chain around the bar. Any roughness must be examined and repaired... the chain must run smoothly on the bar, and the chain must not bee loose... remember 1/16 of an inch and the dogs cannot come out of the slot in the bar.
13. Run the saw, and if it runs properly, go ahead and cut your wood.
14. Check the chain often (every 2 to 3 minutes of cutting) and adjust the chain when necessary. The chain will eventually wear and stretch to where you don't have to check it but every 1/2 hour or so... eventually means about 10 to 15 hours of actual cutting time
If you get into trouble during this procedure, you can look up ""replacing a chainsaw chain" on the web or E-mail me at firstname.lastname@example.org