New Stihl MS261 - uneven chain tension

[Amin_1992]

Hey y'all, this normal for a new chain on a chainsaw?

Got a brand new Ms261 and went to tighten up the chain after checking out the bar. Got it right. Then noticed when turning it, it loosens up, then tightens again. It seems like the chain loosens in two spots. When tight, if I pull it down it clicks back into track with tension. On the loose portions, if I pull up on the chain from the top of the bar, the bottom section of chain pulls taught - release and it drops maybe 1/8 inch.

Normal? Bought a second chain though and it also seems to have tight and loose spots. So either this is a common thing on new chains, or something else is up...

Saw is new. Put half a tank of gas through the first chain, half tank through the second.

How long does it take a new chain to fully stretch and break in? Maybe another full tank should more evenly stretch it?

Unfortunately my dealer service dept kind of sucks and I can see them not seeing an issue...

Is this just normal on pro saws? Don't remember new chains doing this on my MS250...

Thanks guys

 

[Hundred Acre Wood]

https://www.arboristsite.com/threads/tight-loose-spots-new-chain-sprocket-and-bar.366227/

 

[Amin_1992]

Thanks again @Hundred Acre Wood . Unfortunately I've read a few posts like this where nobody gets to the bottom of the answer...

I will say I tried an experiment. In the loosest spot I marked a link and the location on the bar. I then pulled the bar, tried to keep the sprocket in the approximate same spot, turned the chain forward 10 links, then reinstalled. Loosest spot was still at the same marked link/bar location.

I feel like that might eliminate the sprocket as the cause? Possibly points to the chain? Or maybe the bar gear itself since I didn't pull the chain, just slid it?

Is it normal for 2 chains in a row to have tight and loose spots? And how many tanks til it'd loosens up?

As of now I'm going to tighten the chain a bit tighter than I normally would and see if the added tension helps. We'll see.

Unfortunately I'm out of wood for the next few months so no way to get to the bottom of this...

 

[Hundred Acre Wood]

Read Kevin's posts #8 and #11 in that thread. That's the best advice and answer.

 

[KostasVolos]

Read also my post (#49) at the given thread link above .

 

[Amin_1992]

Hey guys thanks for coming in clutch!

So here is where I'm at. I followed what you all had talked about in this posts and then took my guide bar cover off.

I was able to see that the tightness/looseness does in fact seem to correlate to the sprocket! I marked it and every time it got loose, the sprocket was in the same general location (mark was 1 or 2 oclock).

Looking at the sprocket though, it doesnt look like there are any burrs or anything?

Then I looked more closely at the clutch drum. I can see that as I spin it, it is out of round. In the same location, I see the space go up and down between it and the housing.

My next question is this though... I'm not familiar with these separate clutch drums and sprockets (MS250 was one combined unit). Which do you think it is? Or more importantly, is it possible the drum is out of round? Or is this a worst problem - ie, the crank or whatever is spinning the entire assembly is out of round?

I just bought the saw... as I said my dealer isnt all that great. They dont know much. And I already can tell if I drop this off they wont find a problem or will just make it worst and hold my saw for 3 weeks...

I'm ok with just paying out of pocket for a new clutch drum cover and/or sprocket but if that isn't the problem and it's actually the crank then I obviously need to go to them... ugh.

Also, let me ask this: is this a common issue? Is it a big deal? Should I just let it be? Or is this something i need to fix? Maybe Ill try ordering aftermarket drum/sprocket off Amazon to test if it's the issue or not.

Let me know what you all think? It means a lot... thanks

 

[Hundred Acre Wood]

Hey guys thanks for coming in clutch!

So here is where I'm at. I followed what you all had talked about in this posts and then took my guide bar cover off.

I was able to see that the tightness/looseness does in fact seem to correlate to the sprocket! I marked it and every time it got loose, the sprocket was in the same general location (mark was 1 or 2 oclock).

Looking at the sprocket though, it doesnt look like there are any burrs or anything?

Then I looked more closely at the clutch drum. I can see that as I spin it, it is out of round. In the same location, I see the space go up and down between it and the housing.

My next question is this though... I'm not familiar with these separate clutch drums and sprockets (MS250 was one combined unit). Which do you think it is? Or more importantly, is it possible the drum is out of round? Or is this a worst problem - ie, the crank or whatever is spinning the entire assembly is out of round?

I just bought the saw... as I said my dealer isnt all that great. They dont know much. And I already can tell if I drop this off they wont find a problem or will just make it worst and hold my saw for 3 weeks...

I'm ok with just paying out of pocket for a new clutch drum cover and/or sprocket but if that isn't the problem and it's actually the crank then I obviously need to go to them... ugh.

Also, let me ask this: is this a common issue? Is it a big deal? Should I just let it be? Or is this something i need to fix? Maybe Ill try ordering aftermarket drum/sprocket off Amazon to test if it's the issue or not.

Let me know what you all think? It means a lot... thanks

No sprocket is perfect, all clutch drums are out of round. Aftermarket ones are notably worse. We'd need pictures, video, or measurements to put it into context.

My advice is run the saw. Cut wood. You've got a 2 year warranty. Check it again after a few hours, most likely it'll be fine once the sprockets get some wear.

 

[Amin_1992]

@Hundred Acre Wood you're the man my friend. Thanks for constantly helping me out here. I'll do just that!

 

[PV Hiker]

No sprocket is perfect, all clutch drums are out of round. Aftermarket ones are notably worse. We'd need pictures, video, or measurements to put it into context.

My advice is run the saw. Cut wood. You've got a 2 year warranty. Check it again after a few hours, most likely it'll be fine once the sprockets get some wear.

What you can do is have a look at the spur sprocket and your drive links to see if there is any hammering marks.
Also take the chain off and see if you have any wobble play in the sprocket or drum more than normal. This also checks the condition of the roller bearing. This is cheap and easy.

You could take some images of the chain and drive links along with the surface area of the spur sprocket. It is better for us to see what you have as it is quicker for the trained eyes on this board to catch something that you do not see.

here is a image of one of mine ms261 when I picked it up.

 

[Amin_1992]

Thanka @PV Hiker for the reply. I attached a photo similar to yours and also a video showing the out of round movement. Looks to be about +/- 1/16" based on the chain movement. Maybe that's within tolerance?

 

[Amin_1992]

My curiosity got the better of me. Continued my experimentation by marking where the sprocket and drum were positioned when the chain would loosen up, removing bar and chain, and then uninstalling the rim sprocket. I reinstalled it but repositioned it by twisting it 90 degrees first. That way, I could reinstall the bar and chain, turn the chain to the loose spots, and see which part was "in position" - the sprocket or the drum.

Well, looks like it's the sprocket. Chain is in loose position and sprocket is pretty much where it was before, and the drum is in a different position. I'll take the advice here and run with it but for the hell of it I'll order another sprocket and install and see what happens... but this seemed like a pretty easy way to narrow down which part was the culprit

 

[Duane(Pa)]

It’s a damned shame that QC/Tolerances are so sloppy in this day and age! This isn’t some fly by night clone saw. I live with it but don’t have to like it.

 

[PV Hiker]

@Amin_1992 thanks for the image. I was hoping to see the rim sprocket at a 90 degree angle to see the drive link pickups. This is a grab shot off the web.

When you remove the drum are you getting the oil pickup back in the grove?

 

[rupedoggy]

While you have the drum and bearing off, check the crankshaft with a dial indicator for being bent or out of round.

 

[Amin_1992]

Unfortunately I don't have a dial indicator -should get one. I did snap a pic though.

I twisted the rim sprocket again - still loose in same position so I think it's the sprocket. Have a new one on order from dealer so we'll see.

 

[lone wolf]

Unfortunately I don't have a dial indicator -should get one. I did snap a pic though.

I twisted the rim sprocket again - still loose in same position so I think it's the sprocket. Have a new one on order from dealer so we'll see.

So use a stiff fence wire mounted and set it as close as possible and rotate it.

 

[Patrick1903]

Unfortunately I don't have a dial indicator -should get one. I did snap a pic though.

I twisted the rim sprocket again - still loose in same position so I think it's the sprocket. Have a new one on order from dealer so we'll see.

Sprocket is reversible, right?

 

[IntegrityCarpentry]

Hey y'all, this normal for a new chain on a chainsaw?

Got a brand new Ms261 and went to tighten up the chain after checking out the bar. Got it right. Then noticed when turning it, it loosens up, then tightens again. It seems like the chain loosens in two spots. When tight, if I pull it down it clicks back into track with tension. On the loose portions, if I pull up on the chain from the top of the bar, the bottom section of chain pulls taught - release and it drops maybe 1/8 inch.

Normal? Bought a second chain though and it also seems to have tight and loose spots. So either this is a common thing on new chains, or something else is up...

Saw is new. Put half a tank of gas through the first chain, half tank through the second.

How long does it take a new chain to fully stretch and break in? Maybe another full tank should more evenly stretch it?

Unfortunately my dealer service dept kind of sucks and I can see them not seeing an issue...

Is this just normal on pro saws? Don't remember new chains doing this on my MS250...

Thanks guys

This is very interesting you just posted this! I have been having a journey myself and it should help you. Clutch drum may be a minor issue but major reason is the sprocket itself.

How I discovered this. I started working with a guy with your problem just worse. I then had to get parts for my 272xp. Instead of getting just clutch drum bearings I got a whole set of bearings, clutch drum, sprocket etc. instead of getting Chinese I found new old stock oregon set on eBay and bought that. Before I installed it I had no issues with changing tension. The old sprocket was a near mint 4 year old 8 pin Oregon. When I put all the fresh parts on I got the changing tension problem. I took a long time swapping out parts, before I discovered some inconsistency in the pins of the sprocket, changed it to the old one and problem went away. The clutch drum was slightly off, so I went back to my original so only the bearings were new lol.
I have purchased 5 Oregon Sprockets in past couple months and 3 have been bad including 2 I just got last week and just tried to put on a saw today. They looked off, but tried it anyway and they were indeed off. I just pulled 2 from last month out, I need to install them as I might have 4 bad ones lol. The difference will look negligible or slight, but it’s enough. The pins need to be the exact same height and thickness. On some sprockets all the pins are flush with the round edges. On my pictures, the differences shown, are tiny, but it’s enough to be off.

 

[PV Hiker]

Sprocket is reversible, right?

Yes a rim sprocket can be run either direction. Some will see wear and flip it over to get more life out of it.

 

[PV Hiker]

Unfortunately I don't have a dial indicator -should get one. I did snap a pic though.

I twisted the rim sprocket again - still loose in same position so I think it's the sprocket. Have a new one on order from dealer so we'll see.

For some reason to my eye that rim sprocket does not look right where the drive links will pull the chain. Tomorrow some time I'll grab a picture of mine.