I am assuming you know how to adjust the chain's tightness?

I would take it all apart and clean everything out real good, make sure it's got bar oil in the reservoir
and put it all back together, adjust everything just perfect and of course inspect as you go.

You might take a digital picture of it JUST before you put that cover back on as well, that might help us LS'ers.

Then do a lengthy dry run, by dry run I mean don't cut anything with it, just run it while
holding it to various rpm's and don't get your face too close but see what happens.
Like for instance run it at really low rpm to where the chain is just turning and watch it for some time,
see how it's going and all of that, I am pretty sure there has got to be some silly issue someplace that's
causing it, maybe it's a piece of dirt caught in there or...

What's happened to me before is that chain tightening mechanism wasn't in there right,
I'd tighten up the chain just right and wouldn't think nothing of it but it would work itself loose...
Or maybe the cover that holds everything in place broke one of those plastic pegs, who knows...
Again why I would dry run it (and again by dry run I don't mean without oil lol).

Good luck!

 

Thank you for the quick response. I will start to take it apart if no one else has any better ideas. Thanks TopSites

 

what saw is it?

 

Is the bar bent? How is the bar groove and bar rails?

Also, check the drivers, often times if you throw a chain the driver teeth catch on the bar and get bent, or if the chain has been pinched really bad the drive links themselves can be bent. This is especially true with Picco chains and other chains smaller then 3/8"

Try another chain and see if it helps. If it does the same thing to multiple chains, try a different bar.

 

It is a Stihl MS 210 16inch.
The bar and chain are both stihl and both brand new. Where the actual sprocket that spends the chain attached to the actual chainsaw is a little worn.

 

If the sprocket on the clutch is worn, it will cause problems. Replacing it will probably cure the issue.

 

If the sprocket on the clutch is worn, it will cause problems. Replacing it will probably cure the issue.

I will agree that the sprocket is generally what causes chains to jump off. I bet if you llok at yours, you will see deep grooves in it.

 

Cutting hedges or a few small saplings at once will often cause the chain to come off the bar. Does it ever throw the chain when you are cutting solid pieces of wood that are over 2 inches thick? I've never had a saw throw a chain on solid pieces of wood, only when cutting small stuff.

 

Feel the drive links and if they are not smooth then replace the chain and sprocket. When the chain jumps off the drive links take a beating.

Buy a drive sprocket and 2 new chains. When you install a new chain on a worn sprocket the chain instantly stretches so by rotating 2 chains they will all wear evenly. A new bar should be installed when replacing the chains and sprocket.

When adjusting the chain hold up on the end of the bar.

When tightening the bar nuts hold up on the end of the bar.

If you don't hold up on the end of the bar the chain will still get some slack as soon as you begin to cut.

Always break in a new chain by starting the saw and runing it just fast enough for the chain to move slowly. Do this for 3 or 4 minutes. Remember, the teeth travel @ about 50mph under full throttle so in a couple of hours a tooth could travel 100 miles.

Never rev the saw or cut until the chain is broken in. This will give you the maximum life from the bar, chain and sprocket. Treat it like a new chain on an old Harley.

After breaking in the chain let the unit cool for several minutes then adjust the chain because it will have stretched a little bit.

There is absolutely no reason to keep pulling the trigger and reving the saw up and down. The only thing that does is make noise and more money for
the dealers.

Oldtimer

 

Just had the same problem about a month ago and it was the sprocket. Was a $8 fix for mine.

Good Luck,
James

 

Feel the drive links and if they are not smooth then replace the chain and sprocket. When the chain jumps off the drive links take a beating.

Buy a drive sprocket and 2 new chains. When you install a new chain on a worn sprocket the chain instantly stretches so by rotating 2 chains they will all wear evenly. A new bar should be installed when replacing the chains and sprocket.

When adjusting the chain hold up on the end of the bar.

When tightening the bar nuts hold up on the end of the bar.

If you don't hold up on the end of the bar the chain will still get some slack as soon as you begin to cut.

Always break in a new chain by starting the saw and runing it just fast enough for the chain to move slowly. Do this for 3 or 4 minutes. Remember, the teeth travel @ about 50mph under full throttle so in a couple of hours a tooth could travel 100 miles.

Never rev the saw or cut until the chain is broken in. This will give you the maximum life from the bar, chain and sprocket. Treat it like a new chain on an old Harley.

After breaking in the chain let the unit cool for several minutes then adjust the chain because it will have stretched a little bit.

There is absolutely no reason to keep pulling the trigger and reving the saw up and down. The only thing that does is make noise and more money for
the dealers.

Oldtimer

I dont know man I have had more luck by letting them warm up for a min the first time out and thats it. Personally I run them like I stole em and havent let me down yet. The worst thing that happened was the damn tightener nub broke off. Same deal with sleds but thats a different thread

 

If the drivers ain't boogered, and you have everything else in good order, it's gotta be the spur.

Replacements are like 5 bucks and an easy swap. Just an E clip.
While you're in there, grease up the clutch bearing too. It might need replacing if you have never been in there and have worn through a spur...pick one up as well.

Old timer pretty much hit the high notes...

 

Though there are many reasons for a chain to fall off, it's usually due to improper tension or excessive bar flex.

stihl 210 uses a narrow kerf homeowner grade bar & chain, these flex a lot (special the longer versions like your 16"). It's also fitted with a stingy non-adjustible oiler, so a 16" bar chain may run hotter and expand loose.

If adapting to this bar proves difficult, go with a shorter 14", a pro grade or a thicker bar which are all stiffer.

 

thanks guys for the advice. love this site when people give positive and good info.

thanks again.

 

I have a 210, but don't use it much. Over the couple of years, it has been used sparingly, but has worked very well.

This Fall, we had a major windstorm come through. Some trees were uprooted or broken off. One of my customers had a large maple (about 24" across in the main trunk) come down. In the course of working it up, the chain came off. I was surprised, as it had not done so before. But, this was more difficult cutting than I typically do. I was quite sure the chain was properly tensioned. The chain got dinged -- the prongs that run in the grove got damaged enough a few of them would not fit into the groove. I bought a new chain, but later filed down the rough edges and it works fine.

The question still remains, ... just like you, why? I cut far more of this tree with the new chain, without problems. The old chain was not badly worn. Now that I think about, it had not been used enough to warrant a first sharpening. The drive sprocket cannot be worn much, as the saw just does not have many hours.

Mystery...?