# Chain keeps comeing off



## RKDOC (Jun 20, 2006)

I was cutting wood with my Husqvarna 49 chiansaw. Had beeen cutting for about 45 minutes when it threw the chain. I had been checking regularly the chain tension, and adjusting it if needed. When it threw the chain it broke several of the drive lugs on the chain. I checked the drive clutch lugs, checked the bar for dirt or wear, checked the sprocket at the end of the bar, and could find nothing wrong. I removed the chain and put on another chain. With in 3 minutes it threw that chain as well. Again breaking some drive lugs. Does anyone have any ideas what would cause the saw to keep throwing the chain? Everything I have checked fooks fine. (I hate it when MY saw doesn't work)

Thanks for the help


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## 30yearTech (Sep 14, 2006)

From your description, I would say that the drive sprocket and chain you are using do not have the same pitch.


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## RKDOC (Jun 20, 2006)

Thanks 30 year. How do I check the pitch of the drive sprocket? I know the chain because it is stamped on it.

Thanks for the help.


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## 30yearTech (Sep 14, 2006)

RKDOC said:


> Thanks 30 year. How do I check the pitch of the drive sprocket? I know the chain because it is stamped on it.
> 
> Thanks for the help.


Does the clutch drum/sprocket have a part number stamped on it?

What is stamped on the chain?


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## RKDOC (Jun 20, 2006)

Here are the numbers off of the drive sprocket and hub 503 11 93 325 X7, then on the other side of the hub is EM SWEDEN 970523. The drive lug is a 7 tooth that shows very little wear. The number 33 is stamped on the drive lugs of the chains.

Thanks for the help


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## 30yearTech (Sep 14, 2006)

Is your sprocket a "spur" type or "rim" type? 

Could you post a picture of the drive sprocket, the chain with the broken links and the chain bar? 

It sounds like one of the components is mismatched, but the numbers you posted indicate the sprocket and chain are the correct pitch.

33 stamped in the drive link of the chain indicates a .325" pitch .050 gauge chain. The numbers 325 7 on the clutch drum indicates a .325" pitch 7 tooth sprocket. 

However your saw shows to use a .058 gauge chain which would be designated by a 34 stamped into the drive link of the chain. Using a smaller gauge chain in a larger gauge bar may cause the chain to lay over in the bar and possibly have an issue with the sprocket tip in the bar if so equipped, but I am not really sure if that's what is causing it. 

See if you can find the numbers off your bar, and a pictures of at least the chain would be really helpful.


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## RKDOC (Jun 20, 2006)

Here are the numbers off of the bar, SNA 18/45 050/1.3 706 then below that 325 75DL. I have taken some pictures and as soon as my wife ( the computer guru) gets them off the camera and on the computer I will post them.

Thanks for the help


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## RKDOC (Jun 20, 2006)

Here are the pictures, I hope they are what you need. Thanks


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## 30yearTech (Sep 14, 2006)

Everything looks good, the only part that exhibits some wear is the bar. If it were my saw, I would try a new bar. Sprocket looks great, chain displays damage that occurred when chain jumped off and center links were hammered by spinning sprocket. This chain will probably not fit back in a new bar or may bind. 

May want to consider a new chain as well. If you decide to use this chain, you should dress the burrs off the center links so they fit in the bar groove without binding.


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## RKDOC (Jun 20, 2006)

Thanks 30 year. I was planning on replacing the chains. I will replace the bar also. Thanks for the help.


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## 30yearTech (Sep 14, 2006)

Also make sure the auto oiler is working and your getting plenty of lubricant on the bar and chain while cutting. A new chain needs frequent adjustment while it's wearing in for the first 30 mins to an hour of use, check frequently for excess slack.

Best of Luck....


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## duffer72 (Jul 23, 2011)

Just a dumb question but is the chain being put on correctly as the back side of the drive teeth seem to be beat up some and I usually see it when the chain is on wrong. Was it cutting ok before it came off? 

This happens way more often than people admit to, believe me. That is why I came up with something that most people can't forget and tell me later on it helps them put the chain on the right way. Normally on a chain cutter tooth there is what almost looks like a sharks fin, we will call it Jaws, so when the chain is on the saw Jaws always swims toward the end of the bar on the top of the bar.


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## RKDOC (Jun 20, 2006)

Thanks for the help. The chain was cutting great before it came off. I had been cutting for over half an hour before the first chain came off. Maybe two inutes on the second. I will keep and eye on the tension when I use the new chains. Thanks again for all the help.


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## [email protected] (Jan 31, 2010)

Once your chain is on before you start the saw, make sure the chain brake is off you should be able to manually move the chain with minimal resistance. If not then I'd look and see if the bar is pinched or that you have the chain sitting in the drive sprocket correctly. You may already know this stuff though, but if not I hope it helps.
:thumbsup:


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