Drive link damage when chains pop off modern saws

[Curlycherry1]

Ok I understand technology moves forward since I bought my last chainsaw (Stihl 051AV) in 1980. I have a brand new MS660 and my friend has a new MS362. While working cutting the other day his chain popped off and he commented that a few of the drive teeth got damaged and did not fit back into the bar slot. I had never heard of such a thing and I cut firewood professionally trough the 1970s and early 1980s and had probably 1000+ chain pop offs. Even just the other day while working with my friend my chain popped off my 051 and I put it right back on with no problems.

Then while working with my friend with my saw the chain popped off and when I went to put it back on several of the drive teeth were damaged and would not fit back into the bar slot just like he had observed.

So what the heck is causing the damaged? My old saws never, and I mean never had a problem like this and so it has to be something causing it that was not part of the saws in the old days. My brother says it is that metal clip under the bar by the sprocket and he says rip the darn thing out!

So what is causing the damage and how to prevent it? I do not like the idea of having to do a 15 flat file service job on the drive teeth in the woods just to get my saw back up and running.

 

[blsnelling]

It would be very foolish to remove the chain catcher. Besides, it's made of aluminum and would never damage a chain. All you have to do is dress the nick off the DLs and the chain will be fine. I would suspect that the higher chain speeds of todays saw might be a contributing factor. The same B&Cs on his new saws will fit on your 056, so it has nothing to do with the B&C.

 

[volks-man]

i'm with snelling, file it to fit!
high speed is most likely a factor in the damage.


side note: not to challenge someone with experience such as yourself... but i've never had or even seen a chain pop off. are you running them just a tad loose?

 

[Evan]

ive had a few come off. i had one come off my 372 32" bar a few damaged drive links wouldnt fit in the bar groove so i adjust the chain loose enough i could just turn it by hand , then fired up the saw and gave it a few carfull wots.
this knocked the few burrs of the drive links probly put allitle exscesive wear on the inside of the bar groove but got it going in a pinch

 

[sneno77]

Not that uncommon for a chain to come off. Esp if you're cutting trees w/ small, tough limbs and using the top of your bar. One trick that was taught to me during my years on the thinning crew was to put the chain back on and leave it fairly loose. Rev the saw up and the burs are taken care of. Tighten it back up and you're back in business. I realize this isn't the safest option, but it's always worked for me and it's a heck of a lot quicker than trying to use a flat file in the woods.

 

[oldsaw]

File the burrs off and run the chain. If it comes off again, you may have another problem such as a bent bar or the sprocket not lining up with the tail of the bar somehow. Put the bar down on your workbench and put a straightedge on top of it. Also make sure that the grooves are clear on the bar, especially at the tail.

 

[taylor6400]

i'm with snelling, file it to fit!
high speed is most likely a factor in the damage.


side note: not to challenge someone with experience such as yourself... but i've never had or even seen a chain pop off. are you running them just a tad loose?

Never? I have had it happen a few times, and yep, usually cutting small stuff that is in a sideways bind and it just pops it right off. I always went for the file, but its always been just a few links...no big deal. I always figured what nicked the teeth was the bar itself...not the chain catcher.

 

[pinemartin]

To answer your question, on older saws the drive gear is generally a spur type where the teeth are ridged and run the full width of the gear. On a newer saw the drive gear is usually the rim and drum type where the rim has the ability to float from side to side. When a chain comes off these rim and drum systems there is the possibility it can push the rim to one side then ride on the splines of the drum until the saw is shut down. That is the cause of your problem and when shut down quickly the reason there are only a few drive links effected. PS the chain catch is innocent, so listen to Brad and keep the chain catcher on your saw for safety sake.

 

[WoodChuck'r]

A couple of months ago my chain swung off my 7900 due to an idiot move in pinching my bar. The chain hit the chain catcher and the drive teeth (about 12 of them) were garred up pretty bad....

I just filed the edges with my raker file, took about 20 minutes but after that she was as good as new.

 

[blsnelling]

I always though the nicks were wear the chain crossed over the bar rail.

 

[barnumb]

The chain catcher stops the chain immediately and the drive sprocket keeps moving and consequently damages the chain. I have seen this on both drive styles. On my husky 66 if the chain comes off you are filing down torn up drivers. A roller chain catcher seems to help.

 

[Curlycherry1]

side note: not to challenge someone with experience such as yourself... but i've never had or even seen a chain pop off. are you running them just a tad loose?

It popped off cutting some small brush, less than an inch in diameter. That is typically when it has always happened with me. Something in the pile catches it just right and off it goes.

I do probably run a saw chain about 1/8 turn looser than some folks. It comes from what I was taught and what my brother has observed over thousands of cords run on his processor. He has seen that a tight chain wears the bar down faster than if you just back it off 1/8 turn. He of course does not have pop off problems because he never cuts anything but straight cuts.

 

[Curlycherry1]

File the burrs off and run the chain. If it comes off again, you may have another problem such as a bent bar or the sprocket not lining up with the tail of the bar somehow. Put the bar down on your workbench and put a straightedge on top of it. Also make sure that the grooves are clear on the bar, especially at the tail.

Its a brand spanking new saw with 1.5 tanks of gas in it, but just to be sure I put a machinist's straightedge up against the bar while I had it in the shop. I always check my bars for flat when I get the chance to to check them. When I went to get a bar at the local Stihl shop the first one I picked off the rack had a 1/8" gap in the middle as I set it on the bench to pay for it. And it was still in the box! I took it out, laid it down and told the guy he had a problem and he agreed. I got another bar off the rack and it was fine.

 

[pinemartin]

I always though the nicks were wear the chain crossed over the bar rail.

I always thought the nicks were where the chain catcher stopped the chain and the splines on the drum flattened the face of the drive links. If it did happen when a chain crossed over the bar rail you would see this happen on all saws not just the ones with drive rims..

 

[blsnelling]

I've not seen the face of the DL flattened. They were always nicks on the sides.

 

[Curlycherry1]

ive had a few come off. i had one come off my 372 32" bar a few damaged drive links wouldnt fit in the bar groove so i adjust the chain loose enough i could just turn it by hand , then fired up the saw and gave it a few carfull wots.
this knocked the few burrs of the drive links probly put allitle exscesive wear on the inside of the bar groove but got it going in a pinch

I'll confess, that is what I did. Where do I go to get my chainsaw abuser flogging? One quick spin and it dropped right into the track. A few revs and it was warmed up enough to get the perfect tension that I like to have. Adjusting tension on a cold chain is something I do not like to do because once warmed, it often is too loose.

Rant mode on: That chain catch under the bar is a useless part. I already said I had probably over a thousand pop off over my career but never so much as once did I ever have the chain contact my leg, ever. I would love to see any stats that show that was an actual problem.

Kind of like when I was the safety enforcer for my building at work. One day the fire marshall demands all solvent cabinets have self-closing doors. I then pointed out that in over several hundred monthly safety inspections there NEVER was a single case of the doors being cited from being open. Yet the company nurse had something like 18 incident reports of people getting gonked up side the head from cabinets with self-closing doors where their hands slipped and the door closed just as they were looking into the cabinet. Several folks had to get stiches because the lip on the door seal was sharp. That did not deter them and so we had to replace every non-self-closing cabinet, and I got two nice ones for home use for dirt cheap.

I just have a suspision that this 'safety feature' is causing more problems than it is solving.

 

[blsnelling]

Rant mode on: That chain catch under the bar is a useless part. I already said I had probably over a thousand pop off over my career but never so much as once did I ever have the chain contact my leg, ever. I would love to see any stats that show that was an actual problem.

Sounds like a good way to destroy a case or tank/handle. Chain catchers are cheap. Why not use them? Have you ever seen how mangled they can get from catching one chain? That energy has to go somewhere. Why not let if be absorbed by a cheap, inexpensive, replaceable part?

 

[pinemartin]

IT IS NOT THE CHAIN CATCHER DAMAGING YOUR DRIVE LINKS. It is aluminum and only hits the front of the drive links, they are always damaged on the curved back side when the splines of the drum flatten them out. I have slow motion footage of this being the only cause. I don't mean to yell but the chain catcher is innocent.

 

[bitzer]

Chain catchers are there to catch the chain. I think they do mess up the chain on occasions tho. Its metal to metal contact, it doesn't matter how soft the aluminum is. I don't throw chains often, but I've had some flat DL fronts and plenty of swells on the sides. I do like the roller chain catcher for the dual dawgs. It keeps the chain farther out. I've had them slap me in the leg several times, but no injuries.


The easiest way to throw a chain are on what I call "chain skippers," Saplings and small stuff under 5" or so. You cut threw them and they like to push your chain out of the rails if you don't let off on the throttle before you get that far.

I also think the spur type sprockets throw chains more easily than rim. Much more side to side movement.

File off the burs and run them. It sounds like the OP is running chains a little loose, throwing them all the time like that.

 

[Curlycherry1]

Sounds like a good way to destroy a case or tank/handle. Chain catchers are cheap. Why not use them? Have you ever seen how mangled they can get from catching one chain? That energy has to go somewhere. Why not let if be absorbed by a cheap, inexpensive, replaceable part?

Like I said I would love to see the evidence that it actually does any good. Looking at my old 051AV I see no knicks in the cover where the chain would catch when it pops off. That saw has easily 2000+ face cords of wood it has eaten along with well over 2000 lumber log drop and tops. It has probably 5-600 pop offs in its career. Zero damage from chains hitting that part of the cover.

I see on my 660 they have a rubber bumper in the cover in that region to protect the back of the saw should the chain pop off.

I'll leave the chain catch on but I am just not buying it that it is not causing more problems than it is fixing. As a scientist I do see an experiment coming where I might record what happens with it on and then take it off just to see if there really is damage. I just can't let things like this bug me without it being proven to me.