What makes tight chains jump?

[kellysguy]

This Poulan just slung the chain (and into my leg) for the last (admin edit) time! What causes an otherwise tight chain to jump?  Bar wear, clutch wear, a bug in the woods?

[sawguy21]

Have a good look at the bar rails. They may be badly worn or there may be a groove behind the nose sprocket that needs to be dressed out.

[BradMarks]

Not sure your activity, but if it was cutting multiple stemmed brush, that could happen rather easily, tight or not. Sawguy21 is right about the rails, also burrs on the links could contribute.

[beenthere]

How often did that chain jump out? And does it run smooth and then suddenly jump, or do you think it has something to do with using while cutting?

Is the bar groove clean or have packed oil/sawdust in it?

Is the chain bent from previous jumps?

Did it tear up your chaps when it hit your leg or is there blood?

[kellysguy]

Don't know of the chain is bent but will check. No build up in bar. Luckily I'm not cut.

[HolmenTree]

We need a little more information what you were cutting and how you were cutting it.

[kellysguy]

Bay tree limb, about 3-4", cutting straight down but at a 45 degree to the branch (tight spot to cut it 90). I have had problems with it jumping in the past but I've used it lately and it did good. I noticed before the lower dog was bent over and figured that's why it was jumping. With new everything I'm looking at $100 so I'd rather buy a new saw.

[HolmenTree]

Bar with spread rails [ well used laminated bars are famous for that], and the edge taken off one side of the chain can throw a chain easy enough.

[kellysguy]

I hate to dump it because it runs great but I don't want to put anymore money into it.

[fossil]

Worn spur sprockets will cause chains to come off as well.

[sawguy21]

Bars and chains are consumables, they wear out and need to be replaced regardless of saw brand. The chain drivers were were likely damaged when the chain jumped the first time. Did you inspect them and file the burrs off?

[kellysguy]

Inspected and not burred. I really don't have a lot of time on this saw, not enough to throw chains IMO (that's if by driver you mean the links not the sprocket teeth). The clutch bearing is sloppy but I think that's more of a quality issue than anything else. Crank doesn't appear to be bent. The chain is crap and I know that. I don't mind buying a good quality chain but at this point I feel like I am trying to polish a turd.

[John Mc]

Is this the chain that came with the saw originally?  If not, it makes me wonder if perhaps your chain pitch does not match the pitch on your drive sprocket and/or bar sprocket.

The driver is the part of the chain that rides down in the slot in the bar, so named because those little tabs are what engage the slots of the drive sprocket, driving the chain around the bar. One or more drivers are often damaged when I chain gets thrown. If they are not cleaned up, the chain will be more likely to jump off the bar.

If the saw is running fine, it may be time to replace the bar and drive sprocket (along with the chain)

[kellysguy]

If the saw is running fine, it may be time to replace the bar and drive sprocket (along with the chain)

It runs great, the problem is the AV  mount screws keep coming out. One is stripped now and I had to go with a bigger screw. The rubber isolator in the handle fell out along with the screw and Poulan doesn't even show it much less sell it. I've doped it up as best I can (well, actually as best as I care to...) but I'd hate to put almost $100 in parts in a $200 saw that keeps falling apart. I'm tempted to fill the void in the handle with Bondo Hair.

If it was "just a saw" to use around here I'd fix it but I have a decent mill now and feel I need a real saw. I just can't expect myself or anyone else to take me seriously with Fred Sanford's saw. If the darn thing would just stay together long enough to cut it would be an OK little saw.

[John Mc]

I understand. Time to upgrade to something a bit more durable. If that many parts are going bad, it may be time to turn it into a "parts donor" for someone else.

[Grandedog]

    Howdy,
   Considering you weren't into brush, the #1 cause would be a stretched chain.
Regards
Gregg

[beenthere]

??
Chains "stretch"  ??  Have heard this before. 

Slowly wearing and getting longer, I can see.
But that "stretch" is taken up by adjusting the chain bar as the chain droops. 

What else might a "stretched chain" be?

Is it #1 because the operator just lets the chain droop and doesn't snug it up? But if so, I'd say #1 was operator error. ;)

[ZeroJunk]

I seldom get a Stihl in here with any age on it that does not have the the catcher somewhat gouged to almost torn off. I always figured it was more from trying to make one more cut before they retightened the chain or getting the bar twisted on a twig.

[Grandedog]

Howdy,
As the chain stretches, it is changing pitch (distance between drive links). The sprocket wears a little to accept the stretched chain but, eventually the chain will climb the sprocket whether it's on the drive sprocket or, the nose sprocket end.
Regards
Gregg

[KiwiBro]

I seldom get a Stihl in here with any age on it that does not have the the catcher somewhat gouged to almost torn off. I always figured it was more from trying to make one more cut before they retightened the chain or getting the bar twisted on a twig.

Or because they don't break down often enough to never stretch a chain?
;D

[John Mc]

Your saw doesn't by any chance have one of those tool-less chain tensioners on it, does it?

[kellysguy]

Your saw doesn't by any chance have one of those tool-less chain tensioners on it, does it?

No, it's got nuts. I believe a man aughta own a saw with nuts.

[Ox]

I've got a Poulan Pro with a 18" bar.  It was a deal at $75.  I put a new Oregon chain on it because the old chain kept jumping too.  Made no difference.  Kept jumping.  I think it's the POS Poulan bar that comes with the saw.  I haven't gotten around to getting an Oregon bar for it yet.  But it is a pretty good running and starting saw.  I use my Stihl 034av super for everything for now so the Poulan is benched along with 2 other older saws.  The other saws will stay there until something happens to the Stihl and forces me to do something different.

[kellysguy]

I'm torn about fixing it as I do need a backup/ cut my good saw out standby for when I get in a pinch (no pun intended.)

[kellysguy]

Just went and measured:

Bar groove ~.040", chain drive link width ~0.20", chain drive link marked "33". It appears the bar is spreading or worn or whatever. Is the 33 supposed to be 0.33" drive link width?

What's the cheap fix here, squeeze the bar back into spec and square it up with a file or on the belt sander or just get a new bar? What's a good quality bar that will fit?

I wanted to put a Stihl chain on it before it started throwing chains but now I don't know. Honestly I suck at chain filing and need some practice in that area. If I were to fix this thing as a stop-gap till I find the right deal on a 026/260/261, what should I do to make it the best I possibly can for the lowest amount of money? I'm going to need a clutch drum too it looks like or at least the bearing. I really hate to put a new chain on a worn sprocket.

Drum and bearing looks to be around $20

Found a 16" Oregon "Pro 91" bar and chain for around $37 delivered

I don't have anything in the saw to begin with so for around $60 I can have a ok, good running little back up saw that hopefully won't sling chain into my leg again...

Waste of money or would it be a good platform to put a yellow type chain on to get me use to a more aggressive chain?