New Stihl MS 880 CSM keeps throwing chain

[chrispcall]

This is my first post and first foray into milling. I jumped in big time when my father-in-law had a large oak (4ft diameter; 60ft tall) and I decided I wanted that oak for my wood working hobby. I recently purchased an MS880 with 69" bar and a few .404 .063 skip tooth chains. It came with a 36" bar and a standard .404 chain. When using the smaller bar, things seem to go fine and I have successfully cross cut and milled with it. Things are different when I pop on the 5' bar. I try to tension it using the screw on the side of the saw and I can't seem to get it tight enough. Here is my tensioning process:

I set the chain in the sprocket and then install the chain sprocket cover, leaving the nuts loose. I then tighten the screw as much as I can. It gets so difficult to tighten toward the end that I feel like the tensioner "nub" that slides the bar forward is maxed out and unable to move any more. I use a T-handle flat-head to give me maximum torque to tighten it down. Lastly, I set the nose of the bar on a log to provide upward pressure as I tighten the two bolts completely. The chain is taught enough that it is completely seated in the bar all the way around and when I pull up on the chain, I am able to pull it until the entire chain can come out of the bar, but just barely. It feels like it should be just right as I can also slide the chain by hand.

As soon as I start the saw up and hit the throttle, the chain looks pretty loose. Then after milling for about a minute, the chain is so loose that it will throw and pop off the sprocket. It will be visibly out of the bar as it mills and then it will throw. I never have this issue with the smaller bar and again, I tighten the bolts until I can't tighten them any more.

I was unable to verify if the tensioning peg was actually fully engaged so that it could not travel any more and I tried to constantly check tension and tighten the bolts often during our day yesterday but no matter what I tried, I threw that long bar chain after a minute or two of milling. If it is completely bottoming out and has no room left to travel, should I have a link removed and bring the chain from 173 to 172 links so I can tension it properly? Should it be this difficult to tension this long chain and bar? I feel like it can not tighten and the screwdriver wants to slip up out of the tensioning screw. Seems like a bad design to have this screw be a flat-head with the amount of force I have to apply to tension the long bar.

Any help or advice is greatly appreciated. I am pretty frustrated that I bought what I felt would be the best all around setup and am having so many issues. Sorry to be so wordy, I just wanted to ensure I got all of my thoughts out to better explain what was happening.

Thanks in advance!

Chris

 

[Boogedy_Man]

I'm pretty new to this but actually have some of the same questions. I'm running a 661 with a 50" cannon bar, and only did a bit of milling with a shorter bar before giving this a shot. Here's my thoughts:

1. With my saw I find that when I lift the bar the chain actually loosens. You might check into that and consider lifting the bar while working the tensioner and keeping it there while tightening the bolts. Alternatively, maybe my situation has something to do with me running a large mount bar with adapters on a standard Stihl mount....don't know.

2. It seems to me that it requires FAR more tension on a long bar (over 36") than it does a short one. I can't help but wonder if that has something to do with my relative inexperience. I worry about damaging my crank bearings with excess tension. I imagine 69" is even tougher than what I am dealing with. I've been tightening it up a bit after a couple cuts, then loosening it to slack when done (before it cools). Maybe I am over cautious...don't know. I know I'm running enough tension that I can barely rotate the chain with a scrench.

3. In the cut and under load my chain stays in the groove, even when it warms up and tension starts to get a little looser. I try to slow ramp up speed at the start of the cut and be equally cautious coming out at the other end. That seems to help. Beginning and ending, or if the mill gets hung up and the saw races, is when my saw seems mostly like to have chain bounce (or worse yet, throw a chain).

4. I have a double ended bar (adjustment at both ends) so I'm pretty flexible with drive link count. The guy I bought mine from ran 154 links, which worked but had both adjusters nearly maxed out. I went to 153, and that worked but still not a lot of range. I eventually settled on 152 drive links and made 3 chains at that length. I'm pretty sure I could go shorter if I wanted, but I set and forget the saw end and handle it all on the helper handle. If in your shoes, I would probably drop a link.

 

[BobL]

If the adjusters are close to maxed out that's something you need to fix.
Greater than usual tensioning is required for a longer chain
What's happening is your tensioning is not fully removing the slack from every link in the chain, the also chain warms up and expands faster than the bar (I have checked this with an IR temp gauge) and thats what leads to chain drop.
After I tension the chain ay the start of the day I run the saw out of the log for 10-15 seconds, re-tension, an repeated re-tension and run the saw until it stays tensioned

 

[chrispcall]

Thanks for your replies! I guess I will start with BobL's advice and just re-tension it several times right when I start and then see how that goes. If I have no luck with that and the tensioner is maxed out, I will see about removing a link.

Thanks again!

 

[Garrit]

Wow, congrats on the saw and the set up! Here is a video of adding a winch to your mill. Might save your back some day.



Happy Milling!!

 

[SeMoTony]

I'm pretty new to this but actually have some of the same questions. I'm running a 661 with a 50" cannon bar, and only did a bit of milling with a shorter bar before giving this a shot. Here's my thoughts:

1. With my saw I find that when I lift the bar the chain actually loosens. You might check into that and consider lifting the bar while working the tensioner and keeping it there while tightening the bolts. Alternatively, maybe my situation has something to do with me running a large mount bar with adapters on a standard Stihl mount....don't know.

2. It seems to me that it requires FAR more tension on a long bar (over 36") than it does a short one. I can't help but wonder if that has something to do with my relative inexperience. I worry about damaging my crank bearings with excess tension. I imagine 69" is even tougher than what I am dealing with. I've been tightening it up a bit after a couple cuts, then loosening it to slack when done (before it cools). Maybe I am over cautious...don't know. I know I'm running enough tension that I can barely rotate the chain with a scrench.

3. In the cut and under load my chain stays in the groove, even when it warms up and tension starts to get a little looser. I try to slow ramp up speed at the start of the cut and be equally cautious coming out at the other end. That seems to help. Beginning and ending, or if the mill gets hung up and the saw races, is when my saw seems mostly like to have chain bounce (or worse yet, throw a chain).

4. I have a double ended bar (adjustment at both ends) so I'm pretty flexible with drive link count. The guy I bought mine from ran 154 links, which worked but had both adjusters nearly maxed out. I went to 153, and that worked but still not a lot of range. I eventually settled on 152 drive links and made 3 chains at that length. I'm pretty sure I could go shorter if I wanted, but I set and forget the saw end and handle it all on the helper handle. If in your shoes, I would probably drop a link.

I agree with #2 ^ from my experience. What I do, in making my own loops, is to set up the bar w/o cover and make the loop with least amount of DL's. I run oregon which stretches. If you expand my avatar the space between bar and chain at bottom is visible. This after beginning quite snug and cutting only the bit to my left. the fresh loops are a bit a bother to get on the 1st time, but standard ease after the 1st run. The nominal number of DL's printed on the bar doesn't match on every powerhead from Stihl ,for example. Avatar has 60" cannon which was too short to continue down the stump. A 72" dual PH bar should arrive soon if need arizes it will be available.

 

[SeMoTony]

Wow, congrats on the saw and the set up! Here is a video of adding a winch to your mill. Might save your back some day.



Happy Milling!!

Hope that you are not making up for sharp chain with pulling power. Sharp is the most important item followed by b&c lubrication/powerhead tune. If any part of my body hurts after milling something is wrong with the method I used that day. One end of the log higher than the other assists in mill moving down hill. Having the whole log at sufficient height to minimize back bend. My favorite pic of BobLis his seated a few metres to the side of the mill operating on its own. Throttle locked, log on slope, chain sharp enough to "self feed" [ BobL's term] perhap's more than I can see,but no outside direct force on mill.

 

[sawfun]

The Stihl 59" bar flexes a ton, which I don't like as it allows the chain to start to come off. Also I had issues with a that bar and keeping tension on an 880 but not on my 090 for whatever reason. I highly recommend a Cannon 60" over that Stihl bar any day. The Cannon is much stiffer with a similar profile. Now I have not milled with either but have bucked and fallen with them.

 

[SeMoTony]

The Stihl 59" bar flexes a ton, which I don't like as it allows the chain to start to come off. Also I had issues with a that bar and keeping tension on an 880 but not on my 090 for whatever reason. I highly recommend a Cannon 60" over that Stihl bar any day. The Cannon is much stiffer with a similar profile. Now I have not milled with either but have bucked and fallen with them.

Ditto, except I have milled w/60" cannon. Also in another thread 24" bars were run and compared in many ways. Cannon was 1st or 2nd in most, what got my attention was results measuring heat in bar at several areas. Actual temps were shown and the coolness of Cannon's bar seemed to show less resistance to chain flow.
Local store has 880 w/59" bar & the fish tail movement of the bar surprized me when the pair was moved a bit side to side. My milling above 42" bar are all cannon! My 60" cannon has more belly than the Stihl 59".

 

[Butch(OH)]

Ok I am not a chainsaw milling guy but using the Stihl supplied t-handle wrench as tight as one can turn it?? Really? Amazes me that the clutch side bearing lasts long enough to burn the paint off the muffler. I have a 36" bar on my 661 which I realize is a longways from a 60 but the amount of torque required to tension that 36" bar could best be described as limp wristed. I have to tighten the chain AFTER I warm it up out of the cut and I then loosen it when I am done or it gets stupid tight when it cools off. . This procedure is in the manual,,,,

 

[Boogedy_Man]

I think there is a huge difference between a 36 and a 60... With a 661 my tension needs to be just right with a 50" bar, and even when it is any disruption in the RPMs can the chain to come fully out of the upper groove along the whole length of the bar. I imagine with the power of an 880 and yet longer bar its even more of a challenge.

 

[sawfun]

I've found that on the 60" and longer bars, the chain needs to be much tighter than on something like a 36" bar. In horizontal cuts the back of the chain can try to pull away from the bar. This is also why I prefer a deep belly bar like a Cannon as apposed to a pencil profile as in the GB, which is easier to get chain wave on. A Saw with less rpm tends to lessen this as the chain "seems" less wild with fewer fluctuations. Probably since there is a greater chance of issues with much greater chain speed, or less time to act. My 090, 125, or old gear drives do not exhibit near as much chain pulling away or fluxuations (chain wave) compared to what my 088 and 880 did. I would much rather run a torquey long bar saw at 6000 rpm and keep it there than 12,500 rpm or even 9,500 rpm. A saw that makes its power at peak very high rpm, may not be the best long bar saw. I've found a stock 090 makes about as much torque as a well ported 088 but can do it at much less rpm. A ported 090 has low end gear drive like torque. None of this seems to matter until the bars get 60" or longer. I've found a big difference in power requirements between 50 "and 60" with regard to chain speed, likely also bar stiffness.

 

[Butch(OH)]

I have a pretty long bar on my processor and have seen the chain wave you speak of and had to slow my chain speed to get rid of it. Knowing how far the drive rims are from the crankshaft bearings on Stihl saws makes me cringe to think of a chain being as tight as the OP stated, but I guess if ya'll run them that way it must be OK eh? Peterson makes a chain/slabber attachment for their swing mills. I have never seen one in person but watching Youtube vids it would seem that the chain speeds are well under a direct drive chainsaw head?

 

[Boogedy_Man]

"Knowing how far the drive rims are from the crankshaft bearings on Stihl saws makes me cringe to think of a chain being as tight as the OP stated"

I don't disagree at all with that. With the admission that I am very new to this myself, I worry about the same exact thing.

I think the op will probably figure this out by refining his tensioning technique, examining his adjuster, and checking his chain length.

 

[Ted Jenkins]

Bobl is on the right track. Your chain is heating up with in the first few seconds of use, but the bar is not heating up by the same amount. So it will have to be adjusted several times as you use it and it gets warm. The adjuster could be modified to heavier duty bolts, but it takes quite a bit of effort to do so. Yes I have milled a large amount of logs with several different saws, by no means am I the Mr. know it all miller. However have quite a bit of experience with long bars. The shortest bar that will get your job done is the best for these reasons. It is time to make some mods to your set up. Your bar can be ground just a little so that the bar can move as close to the sprocket as possible then you could take out one DL and have more room for adjustment as the chain and bar heat up. Thanks

 

[Boogedy_Man]

Maybe not a know-it-all, but it certainly sounds like you have a lot to contribute on the subject for us newbies. I like the tip about modifying the bar for sure.

What's your take on the too-much-tension concerns? When is enough, enough, and we risk damaging our saws?

 

[Ted Jenkins]

Boogedy you probably will not damage your saw because you have the chain tight, but for me adjust the chain with decent tension then as soon as the chain warms up adjust again. Remember the bearings are sturdy enough to handle all the torque that the engine produces, but there is no reason to risk damage by making the chain so tight it could get into a bind or break. You probably could get by with a smaller bar, but if you are careful you can make it work. Thanks

 

[Boogedy_Man]

Good to know. I don't go berserk with the tension, just noted that it seems to take a heck of a lot more than I expected.

 

[BobL]

Some good info all round coming up - good to see.

I notice a few folks talking about fluctuations and "chain waves" and trying to get rid of it.

My recommendation is not to get rid of the wave because this is how chain cuts.
A chain starts a cuts when the edge of a cutter catches the wood.
The cutter penetrates a little way, slightly lifting the chain off the bar until the raker hits the wood.
The raker then digs in a little which alternately allows the cutter and raker to "rock their way" further into the wood - this further lifts the chain off the bar.

We think of chain as a solid but the forces involved are great enough to temporarily stretch the chain - don't worry steel can stretch a long way multiple times and recover.
When the external tension on, and natural stretch in the chain exceeds the forces needed to tear the wood fibres the cutter snaps back down to the bar pulling out a chip.
Cutter sharpness is less about creating chips by "shaving like a hand plane", and more like creating chips like a jackhammer, where tip sharpness determines the extent of the penetration under the same force.

The chain waves are only few cutters long with only about every 3rd or 4th cutter on a full comp chain generates a big chip, with the cutters behind and in front of the big chip maker making successively smaller or no chips. The chain effectively porpoises or sets up a wave in the kerf. If the cut width and RPM are just so, the waves may be are synchronized and this is what causes washboarding.
At other widths/RPMs there are more/unsynchronized waves, so no washboarding.
Sometimes you can see the wave coming out of the kerf on the cutting side of the bar when the chain heats up and gets a bit longer.
There is nothing wrong with that provided the wave amplitude does not get too large because that is a sign the chain is realy getting loose.

To allow the chain to generate the cutting waves, it's better not to set the tension to "rock hard"
If you set it rock hard the chain will still attempt to make the waves by stretching the chain itself perhaps beyond its elastic limit.
This will lead to all sorts of wear and tear issues.

Using the standard thumb and forefinger test to see how far the chain comes away from the bar is not really a chain tension test, its just basic test of the amount of slack in the chain.
Like I said above, chain is designed to and works by repeatedly stretching.
Chain is a bit like a steel wire or bungee cord, a short piece only safely stretches and recovers back to its original length a short amount.
Short bars usually are used on small power heads which don't always have enough torque to stretch a chain to form a wave so chains are given a bit of slack so they can create the cutting waves.
Longer chains can safely stretch much further (without exceeding their elastic limit) and this is what is used to set up more waves in a cut, and is why a long chain still cuts well even with what we think of as higher initial chain tension.
You can remove all the slack from a long chain and add extra tension on top of that and it will still cut well.

On top of all this the chain gets hot and expands and a longer chain will of course expand further and become loose until the bar warms up and expands as well which is where the initial higher tension helps hold a longer chain on the bar.

 

[SeMoTony]

Some good info all round coming up - good to see.

I notice a few folks talking about fluctuations and "chain waves" and trying to get rid of it.

My recommendation is not to get rid of the wave because this is how chain cuts.
A chain starts a cuts when the edge of a cutter catches the wood.
The cutter penetrates a little way, slightly lifting the chain off the bar until the raker hits the wood.
The raker then digs in a little which alternately allows the cutter and raker to "rock their way" further into the wood - this further lifts the chain off the bar.

We think of chain as a solid but the forces involved are great enough to temporarily stretch the chain - don't worry steel can stretch a long way multiple times and recover.
When the external tension on, and natural stretch in the chain exceeds the forces needed to tear the wood fibres the cutter snaps back down to the bar pulling out a chip.
Cutter sharpness is less about creating chips by "shaving like a hand plane", and more like creating chips like a jackhammer, where tip sharpness determines the extent of the penetration under the same force.

The chain waves are only few cutters long with only about every 3rd or 4th cutter on a full comp chain generates a big chip, with the cutters behind and in front of the big chip maker making successively smaller or no chips. The chain effectively porpoises or sets up a wave in the kerf. If the cut width and RPM are just so, the waves may be are synchronized and this is what causes washboarding.
At other widths/RPMs there are more/unsynchronized waves, so no washboarding.
Sometimes you can see the wave coming out of the kerf on the cutting side of the bar when the chain heats up and gets a bit longer.
There is nothing wrong with that provided the wave amplitude does not get too large because that is a sign the chain is realy getting loose.

To allow the chain to generate the cutting waves, it's better not to set the tension to "rock hard"
If you set it rock hard the chain will still attempt to make the waves by stretching the chain itself perhaps beyond its elastic limit.
This will lead to all sorts of wear and tear issues.

Using the standard thumb and forefinger test to see how far the chain comes away from the bar is not really a chain tension test, its just basic test of the amount of slack in the chain.
Like I said above, chain is designed to and works by repeatedly stretching.
Chain is a bit like a steel wire or bungee cord, a short piece only safely stretches and recovers back to its original length a short amount.
Short bars usually are used on small power heads which don't always have enough torque to stretch a chain to form a wave so chains are given a bit of slack so they can create the cutting waves.
Longer chains can safely stretch much further (without exceeding their elastic limit) and this is what is used to set up more waves in a cut, and is why a long chain still cuts well even with what we think of as higher initial chain tension.
You can remove all the slack from a long chain and add extra tension on top of that and it will still cut well.

On top of all this the chain gets hot and expands and a longer chain will of course expand further and become loose until the bar warms up and expands as well which is where the initial higher tension helps hold a longer chain on the bar.

Thank you Bob for painting the picture in my head (-;