Stupid amount of chain stretch?

[RED-85-Z51]

Oregon chain stretch more than Stihl.
One thing you could do is on your chains that have stretched is remove a few links with a breaker/spinner to get it back to the right size

Thats not normal though. Its completely abnormal to have to shorten a chain after a few tanks because its stretched to the limit.

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[magnus333]

I just had the saw out in the garage. Shaft seems solid as a rock, the bearing seemed fine, everything moved and was solid. So I moved on to tension up the saw snug to sharpen and noticed the chain sags about 1/8 of an inch every 8th link. At first I figured it was the new china 8 tooth sprocket I just put in to get ever so slightly more play out of the chains before taking a link out.
Upon closer inspection it seems like something is wrong with the alignment between the retaining washer/clip and the sprocket, or possibly the clutch. Visibly everything looks perfect to my untrained and somewhat blind eyes, but when I had the retaining washer/clip in, the chain sagged every 8th link. When I had it out, it ran smooth. I tried a newer 7 tooth as well and it wasn't smooth when the retaining clip was in either.

I actually remember reading about someone who had a similar problem, as if his clutch was 1/16th of an inch further into the saw than it should have been forcing the sprocket to oscillate a little and he also had infinite chain stretch. I think he put a washer behind the sprocket or something, I can't remember.

Regardless, this constant hammering of the chain every 8th link makes a lot more sense to me than oil being too light or heavy. Now the question is, how to fix it.

Also, while I was out in the forest I do recall several occasions where the chain felt a little stuck and I had to force it free while sharpening. I assumed it was just bark or something caught in there but now I think it was this alignment issue.

 

[PV Hiker]

Got any pictures?

 

[PV Hiker]

Just throwing out random ideas....

you took the rim sprocket and drum off and the bearing looks fine and lubed?

You did not notice the drum housing being bent using a straight edge.

The rim sprocket holes accept the drivers on the chain fine? Check drive links for any that are miss match.

The drum went back on the shaft/bearing all the way and the oiler pump wire set into the drum Grove allowing the washer and e clip to be properly in the shift Grove.

Without bar hand spin should see if the drum and rim sprocket has any wobble. Make sure all the case holding screws are tight.

The tail of the bar have any bad wear or bent showing?

 

[magnus333]

Just throwing out random ideas....

you took the rim sprocket and drum off and the bearing looks fine and lubed?

You did not notice the drum housing being bent using a straight edge.

The rim sprocket holes accept the drivers on the chain fine? Check drive links for any that are miss match.

The drum went back on the shaft/bearing all the way and the oiler pump wire set into the drum Grove allowing the washer and e clip to be properly in the shift Grove.

Without bar hand spin should see if the drum and rim sprocket has any wobble. Make sure all the case holding screws are tight.

The tail of the bar have any bad wear or bent showing?

Bearing looked good.

Drum was perfectly flat as far as I could tell.

Rim sprocket holes did accept drivers fine, if the retainer was off.

Drum and bearing went on fine. The issue seems like it's on the other end as if the rim sprocket needs to go about 1/16th away from the saw to line up with the bar properly. I think a thinner washer might work in my case.

There IS some slight wobble if I depress on either side of the drum, I honestly can't see any when I spin it freely though.

I used 2 different bars so bar doesn't seem to be the issue. It's not terrible or bent, but it's not new either. I think it's got maybe 20 hours on it?


I could take pics but I don't know what I'd take them of, it looks fine to the eye. It's so very slight. Also this would explain my rim sprocket wear which has been worse than I'd expect.

 

[farmer steve]

Didn't see any mention of the needle bearing. In good condition?

 

[deye223]

What brand of rim sprockets are you using.
Chinese ones nearly always have the centre spline hole of centre , I will use nothing but stihl because of a similar problem 10 years ago.
Easy to tell when the chain has enough slack that half-way along the bottom of the bar the drivers are just clear the groove as you grab hold of the chain and move it you watch it go up and down and nearly slaps the bottom of the bar.
At speed undercutting conditions this belts the crap out of the crank bearings and the chain obviously that causes all sorts of problems.

 

[Westboastfaller]

I will use nothing but stihl because of a similar problem 10 years ago.

Something is not true on the moving parts as he says it drops about an 1/8 every revolution of the engine.
Sounds like you are saying it gets tight every revolution or half revolution as that's what I would suspect it would do if that was the case with that kind of sprocket.
Yeah in 2008 my Mechanic/builder got a batch of them. They were described as oval shape. I have heard people talk about them on here also some years back as well.
So the centre was actually off were they.

It almost sounds like he is saying that it just instantly drops each revolution to 1/8 sag.?

 

[deye223]

I still have some here and measuring with a dial caliper it's the hole that is off centre the outside is perfectly round where the chain runs but it's the hole in the centre that goes on the spline of the clutch drum it's off centre on the ones I have any way

 

[Westboastfaller]

That makes more sense to me.
I remember 'Mechanic Jonny' was saying you could actually see that they were out of round with the naked eye. Quite possibly 2 separate f* ups.

 

[Jay Hansen]

Given your description of the sprocket not quite being aligned with the bar groove, I think I would try a spur sprocket. That would allow the chain drivers to ride right against the washer, and bring it more into alignment. . Its also probable that the spur will maintain a truer pitch throughout it's life.
Under the conditions you describe, it seems that carbide tooth chain would be beneficial. It probably won't stretch less, but you'll spend a lot less time sharpening.

 

[Westboastfaller]

The issue seems like it's on the other end as if the rim sprocket needs to go about 1/16th away from the saw to line up with the bar properly. I think a thinner washer might work in my case.

If it' gets loose on every engine revolution then it's certainly not the chain. Examples:
A very tight master link will give you a tight chain every time it goes over the sprocket. Not to mention a vibration. It wouldn't be as noticeable on an 8 tooth as it would a 7 T
What you wrote would rule out any pomssible bar issues also.

Are you sure the sprocket just hadn't trailed
fully into line yet since putting the chain back on? Try pushing it out with your bar wrench.

Anyway, as said, examine those sprockets.
You said they are Chinese?
Try stay away from that aftermarket crap or get some advice on some of the brands that has been good.

You will cause yourself a lot of unnecessary problems.

Maybe the washer is slightly bent or it's not the correct one or the correct clip?
Research that.

Chain could be pulling down the drum and leaning the bottom of the sprocket inwards towards the saw and that is why it can not come In further at the top ("line up")
I would also revisit the clutch drum and see if it's oval shaped and has more play than it initially appeared? Maybe the spine on the drum is not true? (Not likely)
Possibly the ID or OD of the bearing is wrong? IDK? (Not likely)
It's only a handful of things it can be.
You just have to start at the easiest and work your way in and hopefully it's a NOT a PTO bearing or a bent crank.
You don't want to keep running it in the cost of taking out a top end too.
You need to be right, here.. The washer may be what it is binding on but if it is in fact the correct healthy clip & washer then that suggests you have a problem somewhere else?

You are on the right track, I do believe.

Have you always owned that saw since new?

 

[Timber MacFallen]

The adjuster isn't backing off, the chain is stretching. A new one hangs about 1 inch lower on a nail compared to a stretched one.


Yeah the dust is from dirt, it's high desert here, nearly zero humidity. Every foot step kicks up a waft of dust. The trees are coated in it in addition to all the critter debris that get caught in the shaggy bark, also many trees have significant rot in the stumps (which I need to remove per my commercial permit specs). I didn't mention it before but cutting a decent stump (30-36"), even in a single short cut basically stretches the chain from perfectly tightened to falling off the bar in about 30 seconds and it doesn't come back from cooling (still only 95F after the cut). I try to sweep stumps off on the outside as much as possible, only to find a den of dirt and decomposed rot in the middle 65% of the time.

So that seems like it could be it. But what do i do about it. Maybe strained motor oil is the way to go and up my oil to gas ratio considerably coating the forest service in a thin layer of EPA approved sludge!??!

What is your bar length and are you using a solid or roller tip?

Can you confirm that if you put a sheet of paper or newspaper in front of the bar and rev the saw you're getting a steady spray of oil onto the paper?

Using lots of oil doesn't mean it's going where it needs to.

You are using a powerful saw. What chain gauge and pitch are you running?

 

[SteveSr]

Bearing looked good.

Drum was perfectly flat as far as I could tell.

Rim sprocket holes did accept drivers fine, if the retainer was off.

Drum and bearing went on fine. The issue seems like it's on the other end as if the rim sprocket needs to go about 1/16th away from the saw to line up with the bar properly. I think a thinner washer might work in my case.

There IS some slight wobble if I depress on either side of the drum, I honestly can't see any when I spin it freely though.

I used 2 different bars so bar doesn't seem to be the issue. It's not terrible or bent, but it's not new either. I think it's got maybe 20 hours on it?


I could take pics but I don't know what I'd take them of, it looks fine to the eye. It's so very slight. Also this would explain my rim sprocket wear which has been worse than I'd expect.

Bolt the b & c on without the clutch cover. That way you can see what lines up and what doesn't. Anybody want to wager that this is an AM drum/sprocket that has the wrong dimensions? The other thing to check is that the interface between the saw and bar is PRISTINE clean! Crud in here will mess up both alignment AND oiling!

 

[SteveSr]

Given your description of the sprocket not quite being aligned with the bar groove, I think I would try a spur sprocket. That would allow the chain drivers to ride right against the washer, and bring it more into alignment. . Its also probable that the spur will maintain a truer pitch throughout it's life.
Under the conditions you describe, it seems that carbide tooth chain would be beneficial. It probably won't stretch less, but you'll spend a lot less time sharpening.

Possibly severe SIDE loading of the chain due to alignment issues would likely wear the chain in short order. Chain should be in alignment with ZERO side loading. This is another advantage of the floating spur sprocket.

 

[magnus333]

What brand of rim sprockets are you using.
Chinese ones nearly always have the centre spline hole of centre , I will use nothing but stihl because of a similar problem 10 years ago.
Easy to tell when the chain has enough slack that half-way along the bottom of the bar the drivers are just clear the groove as you grab hold of the chain and move it you watch it go up and down and nearly slaps the bottom of the bar.
At speed undercutting conditions this belts the crap out of the crank bearings and the chain obviously that causes all sorts of problems.

I've only used stihl 7tooth until now. Though I had planned to try a china 8 tooth today.
I measured the distance from the inside to outside on the stihl rim sprockets just now and it was exactly 6mm on every tooth. They don't appear to be out of center visually or by measure.

It almost sounds like he is saying that it just instantly drops each revolution to 1/8 sag.?

Yes, using a new 8 tooth rim sprocket every rev the chain drops 1/8 off the bar for a single tooth worth of revolution and then comes back to snug immediately for the next 7. I don't have any new 7 tooth rim sprockets to test with, only worn ones, but it was similar with a warn one.

Are you sure the sprocket just hadn't trailed
fully into line yet since putting the chain back on? Try pushing it out with your bar wrench.

Maybe the washer is slightly bent or it's not the correct one or the correct clip?

Chain could be pulling down the drum and leaning the bottom of the sprocket inwards towards the saw and that is why it can not come In further at the top ("line up")
I would also revisit the clutch drum and see if it's oval shaped and has more play than it initially appeared? Maybe the spine on the drum is not true? (Not likely)
Possibly the ID or OD of the bearing is wrong? IDK? (Not likely)

Have you always owned that saw since new?

I loosely pushed the rim sprocket out towards the washer before running the test. If I really force it I can get the intermittent sag down to possibly 1/16th instead of 1/8th, but that's not 0.

My thought this morning was that it was the wrong washer since I saw some thinner looking ones on youtube and ebay but it appears to be correct when looking up the OEM part images. My washer is on the right. It's flat against a straight edge. The rim sprocket on the left has around 3-6 tanks of gas on it. I have no idea if that's typical wear for such little use, but I doubt it.

I did buy the saw new, no one else has ever used it. In fact, I've barely used it and I think I've had this issue since day one.

I'm going to head to the dealership today and grab a new bearing, drum, washer and see if they have a spur socket I could try. The only remaining thing that seems likely is the chain pulling the drum and leaning the sprocket. The STIHL rim sprockets do seem to have a lot of play (easily able to create an oval trajectory) but that should self-correct I would think. I carefully measured the drum spine but it was perfect.

I've bent a crank before and broken another on some mowers back when I had a lawn business years ago. That takes an extraordinary amount of force and the saw hasn't been exposed to anything even remotely like that so I don't know how that would have happened. I rotated the drum a lot by hand watching the gap between the plastic and drum and it never changed. I would think that gap would get bigger and smaller if it was a bent crank.

Thanks again for all the help!

 

[SteveSr]

I've only used stihl 7tooth until now. Though I had planned to try a china 8 tooth today.
I measured the distance from the inside to outside on the stihl rim sprockets just now and it was exactly 6mm on every tooth. They don't appear to be out of center visually or by measure.


Yes, using a new 8 tooth rim sprocket every rev the chain drops 1/8 off the bar for a single tooth worth of revolution and then comes back to snug immediately for the next 7. I don't have any new 7 tooth rim sprockets to test with, only worn ones, but it was similar with a warn one.



I loosely pushed the rim sprocket out towards the washer before running the test. If I really force it I can get the intermittent sag down to possibly 1/16th instead of 1/8th, but that's not 0.

My thought this morning was that it was the wrong washer since I saw some thinner looking ones on youtube and ebay but it appears to be correct when looking up the OEM part images. My washer is on the right. It's flat against a straight edge. The rim sprocket on the left has around 3-6 tanks of gas on it. I have no idea if that's typical wear for such little use, but I doubt it.
View attachment 873322
I did buy the saw new, no one else has ever used it. In fact, I've barely used it and I think I've had this issue since day one.

I'm going to head to the dealership today and grab a new bearing, drum, washer and see if they have a spur socket I could try. The only remaining thing that seems likely is the chain pulling the drum and leaning the sprocket. The STIHL rim sprockets do seem to have a lot of play (easily able to create an oval trajectory) but that should self-correct I would think. I carefully measured the drum spine but it was perfect.

I've bent a crank before and broken another on some mowers back when I had a lawn business years ago. That takes an extraordinary amount of force and the saw hasn't been exposed to anything even remotely like that so I don't know how that would have happened. I rotated the drum a lot by hand watching the gap between the plastic and drum and it never changed. I would think that gap would get bigger and smaller if it was a bent crank.

Thanks again for all the help!

That sprocket looks terrible! Is it the correct pitch for the chain and the bar? And yes, a bad sprocket will also wear out a new chain in short order. Take the whole pile to the dealer and hope that he knows how to sort this out.

 

[magnus333]

That sprocket looks terrible! Is it the correct pitch for the chain and the bar? And yes, a bad sprocket will also wear out a new chain in short order. Take the whole pile to the dealer and hope that he knows how to sort this out.

You should see the blurry sprocket behind it that had 10 or 15 tanks go through it. This one looks very good by comparison. It's the correct pitch.

I only have 3 days left on my permit to clear my lot and I've got a ways to go thanks to this nonsense. Commercial clearing permits are really rare here so I need to make the most of it with what i have. But if I can't fix it today, come Monday the whole thing will go in.

Also I've gone through 3 cans of carb cleaner in the last 2 days on this saw. I've been keeping it extremely clean and flush. Meanwhile the china-choppa! hasn't seen a single drop of cleaner in years and works great...

 

[HarleyT]

When replacing a shot sprocket, one should also replace the chains. As running the damaged old chains will quickly damage the new sprocket.

 

[1289]

Take a video and link here