Stihl 661 chain keeps coming loose

[rumrun999]

Morning fella's, just looking for some advise on keeping my 661 chain tight. I have reviewed almost all of the articles on Arborist to see all the tips on setting up and keeping the chain tight, tip up, cleaning, etc. My question is, what is the actual torque number for the bar nuts, I thought I read it was 17NM or about 34 ft lbs? I use the stihl wrench and am almost afraid of pulling a bar stud out. For bucking, I undercut about 60-65% of the time, so I have to wonder if keeping the tip up is counter productive. To verify I have all my parts in order from the crank case out, it is the stainless deflector, the bar, then the clutch cover with the integral bar nuts. There is no stainless deflector between the clutch cover and bar, correct? I always keep a super sharp chain and lean on the saw pretty hard, but not to impede the max cutting speed coupled with engine rpm.

Thanks for your time

 

[HarleyT]

Put up a pic of your sprocket. I am guessing that it is worn out...

 

[rumrun999]

I will do that tomorrow, my guess is I have no more than 50 face cord on the original bar, chain and sprocket.

The saw is less than 2 years old. Thank You for the reply.

 

[HarleyT]

It is classic symptoms of a worn out sprocket, but of course if you replace the sprocket, you should get 2 new chains, and not use your old chain.

 

[rumrun999]

Here are some pic's. Thanks for all of your insight.

 

[rupedoggy]

Those studs have a long shoulder. Make the depth on the cover a little deeper. They may be bottoming out and keeping you from getting it snug. Some of the late model saws have a thicker side plate also. The bar may be a little thinner than some also. Check all that. Mike

 

[rumrun999]

I will check that out, thanks

 

[Bwildered]

Morning fella's, just looking for some advise on keeping my 661 chain tight. I have reviewed almost all of the articles on Arborist to see all the tips on setting up and keeping the chain tight, tip up, cleaning, etc. My question is, what is the actual torque number for the bar nuts, I thought I read it was 17NM or about 34 ft lbs? I use the stihl wrench and am almost afraid of pulling a bar stud out. For bucking, I undercut about 60-65% of the time, so I have to wonder if keeping the tip up is counter productive. To verify I have all my parts in order from the crank case out, it is the stainless deflector, the bar, then the clutch cover with the integral bar nuts. There is no stainless deflector between the clutch cover and bar, correct? I always keep a super sharp chain and lean on the saw pretty hard, but not to impede the max cutting speed coupled with engine rpm.

Thanks for your time

You should never be leaning on a saw hard, if you are then either the chain isn't sharp or the depth gauges aren't set right, more pressure means more heat, which will mean a lose chain, your drive sprocket is fine.

 

[gorman]

Morning fella's, just looking for some advise on keeping my 661 chain tight. I have reviewed almost all of the articles on Arborist to see all the tips on setting up and keeping the chain tight, tip up, cleaning, etc. My question is, what is the actual torque number for the bar nuts, I thought I read it was 17NM or about 34 ft lbs? I use the stihl wrench and am almost afraid of pulling a bar stud out. For bucking, I undercut about 60-65% of the time, so I have to wonder if keeping the tip up is counter productive. To verify I have all my parts in order from the crank case out, it is the stainless deflector, the bar, then the clutch cover with the integral bar nuts. There is no stainless deflector between the clutch cover and bar, correct? I always keep a super sharp chain and lean on the saw pretty hard, but not to impede the max cutting speed coupled with engine rpm.

Thanks for your time

Replace the cage bearing the goes over shaft.

 

[Derrick Sawyer]

Dude did you just start using this saw or for a long time? Did it have this problem before? Get the long scrench for the saw,even if it has the torx end, for tightening those bar nuts. Get the chain decent tight while lifting the bar up with your other hand. Make sure it is oiling good since it will loosen if chain is run dry. In your pic of the bar studs, the chain tensioner is all the way loose, is that how its adjusted on the saw? All the way left?

 

[Canyon Angler]

My question is, what is the actual torque number for the bar nuts, I thought I read it was 17NM or about 34 ft lbs?

First, where are you getting this figure? I've never seen a torque spec for the clutch cover nuts, but 34 ft-lbs sounds insanely tight to me.
To get 34 ft-lb with a 6-inch scrench would require you to lift a 70-pound sack of lead bricks.
Are you standing on your chainsaw when you put this 10' pipe on your scrench handle?
Second, 17 Nm is not 34 ft-lbs – it is 12.5 ft-lbs. When you use your 6" scrench, just imagine lifting a 25# bag of bunny food.
12.5 ft-lb sounds more like it, and is about what I use – and never have a problem with bars falling off, chains getting loose, or bar studs breaking.
Try this: With the saw in your left hand, press the tip of the bar down onto a piece of scrap wood on the floor, and with your right hand, tighten the bar nuts with your scrench. Then check your chain tension. This method has always worked for me...

 

[smokey7]

But if he under-cuts 90% of the time maybe keeping the bar down would treat him best? Id be tempted to find some thin wall tubing and make some sleeves for the studs to eliminate as much bar slop as possible. I suspect if he kept the bar down when tightening it would help lessen his issue plus if it does get loose a down cut should fix it right up lol.

 

[Little Al]

If you have been tightening the bar studs to 34ft lbs the thread oud have stretch a tiny bit to allow the nuts to bottom out on the plain stud shank a couple of washers under the nuts or a die & another couple of threads on the studs make sure the bar tensioner is properly engaged & working properly

 

[rumrun999]

I have used the saw since new. The chain loosening has been something new and recent over the last 3 to 4 loads of wood. The bar tip is always up on a piece of wood and I do not tighten to 34 ft lbs, I was just looking for a reference. The clutch cover fits over the stud shoulders to not impeded tightening. I picked up a new sprocket, the old one was stamped 3 AB and the new one is 2 AR or vise/versa and I have a new chain to go with the new sprocket and will check the cage bearing while I am in there. I will post when I have a chance to cut again and thank You for all the tips.

 

[rupedoggy]

New chain will stretch a little at first

 

[trains]

Could be a silly question, but has the oil hole in the bar become clogged, causing less oil, more heat, and thus chain coming loose ?
As your doing all the same things, and something new has started, thought I would mention it.

 

[rupedoggy]

i never had a chain get loose from no oil but I sure had them get tight. Mike

 

[trains]

Ive had both happen, fine dust/ chips from redgum blocking the oil hole, chain got sloppy on the bar.
On my 009s, the oiler stopped working, chain went tight before I realised what had happened.

 

[Wood Doctor]

My logger buddy runs his 661 with a 30" to 36" bar and the chain always tends to run loose after awhile. He says, "That's the way it is. Chains stretch on long bars, especially new chains. I tighten up after every tank of fuel and sometimes more often. Simple as that."

 

[Canyon Angler]

Don't forget to loosen the tension on a big, hot chain when you put away the saw. Just as they lengthen when they heat up, they shorten when they cool off – and you don't want mega tension on the crank when you put the saw away.