Changing Bar Pitch on Stihl MS261

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HappyHomeowner

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Hi folks, I've seen similar threads but I would appreciate some specific advice from the experts regarding something I saw in the manual to my new to me MS261. I might be overthinking things but before I screw something up, I figured it is better to ask the experts here.

I just purchased a Stihl MS261 originally equipped with a 20" Bar in a .325 Pitch at an authorized Stihl Dealer.

I have several other saws by Stihl including an older MS 291 with a 20" Bar in a 3/8 Pitch and .050 Gauge.

I asked the dealer if it was possible to put a 20" Bar in a 3/8 Pitch, .050 Gauge on my new MS261 so that I could continue using the chains that I use with my MS291.

They were very wonderful about it and put a 20" Bar in a 3/8 Pitch, .050 Gauge (Stihl Part 3003 000 8822 if that matters) on my new MS261 so I could continue using all my 20" Chains (they are all Stihl Part 33 RSC3 72 if that matters). I have not yet used the saw because I just read in the manual the recommended pitch for the 261 for all the assorted bar and chain combinations is .325. They don't technically list any other combination other than with the .325 pitch.

Is there a problem with putting a Stihl 20' Bar in a 3/8 Pitch on my new MS261? I'm thinking this is just in the manual because all the saws are sold originally equipped with the .325 pitch and not because another pitch is incompatible but again before I run it I thought I ought to ask. Maybe the sprocket or something else somehow makes this a bad idea? Or maybe as usual I'm overly overthinking things! :) I appreciate your assistance.
 

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Hi folks, I've seen similar threads but I would appreciate some specific advice from the experts regarding something I saw in the manual to my new to me MS261. I might be overthinking things but before I screw something up, I figured it is better to ask the experts here.

I just purchased a Stihl MS261 originally equipped with a 20" Bar in a .325 Pitch at an authorized Stihl Dealer.

I have several other saws by Stihl including an older MS 291 with a 20" Bar in a 3/8 Pitch and .050 Gauge.

I asked the dealer if it was possible to put a 20" Bar in a 3/8 Pitch, .050 Gauge on my new MS261 so that I could continue using the chains that I use with my MS291.

They were very wonderful about it and put a 20" Bar in a 3/8 Pitch, .050 Gauge (Stihl Part 3003 000 8822 if that matters) on my new MS261 so I could continue using all my 20" Chains (they are all Stihl Part 33 RSC3 72 if that matters). I have not yet used the saw because I just read in the manual the recommended pitch for the 261 for all the assorted bar and chain combinations is .325. They don't technically list any other combination other than with the .325 pitch.

Is there a problem with putting a Stihl 20' Bar in a 3/8 Pitch on my new MS261? I'm thinking this is just in the manual because all the saws are sold originally equipped with the .325 pitch and not because another pitch is incompatible but again before I run it I thought I ought to ask. Maybe the sprocket or something else somehow makes this a bad idea? Or maybe as usual I'm overly overthinking things! :) I appreciate your assistance.
You can easily swap it out to 3/8
Either run the spur style
Or a rim kit.

Personally I tried 3/8 on my 261 290/310/390
And always went back to .325
I cut primarily hardwoods.
 

HappyHomeowner

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You can easily swap it out to 3/8
Either run the spur style
Or a rim kit.

Personally I tried 3/8 on my 261 290/310/390
And always went back to .325
I cut primarily hardwoods.

Thank you so I swap the .325 sprocket (rim) with a 3/8 sprocket (rim) and I am GTG? Thank you again.

PS, EDIT: I guess I'm confused why the dealer didn't do that when they swapped the bar. Thank goodness I actually read all through the manual! :)
 

HappyHomeowner

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Thanks again do the amount of cutters on the chain matter at all to the sprocket? In other words the MS261 originally had 81 cutters and my MS291 chain has 72 cutters. Does that make any matter to the sprocket or is it just the pitch that matters? Thanks. Also the "sprocket" on my 291 is different in the sense that it is part of the clutch brake cover whereas with the 261 it is a part separate from the clutch brake cover ( I hope I am using the correct terms here I can take a picture if that helps. Thanks again.
 
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Where is @Philbert when we need him and his excellent explanatory graphics?
I can still remember being as mystified as you are by all the numbers and terminology. Most importantly, to function properly, the chain, bar, and drive sprocket must "mesh." Running .325 chain will require a different sprocket and bar (I'm assuming hard nose bars are not in consideration) than running 3/8 (.375) chain. The .325 links are shorter in length than the .375 links, so more of them are required for a given bar length. That's why the 20" .325 bar wants 81 while the 20" .375 bar needs only 72.
There is also the complication of drive sprockets/drums. The one piece drum type is generally called a spur sprocket. The two piece variation has a drive rim that slides on to the spline on the drum. Most important is that the drive components are sized to agree with the chain size.
 

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The drive sprocket, guide bar, and chain work as a ‘system’: they must all be compatible: Pitch, Gauge, Drive Link Count. Change one component and you may have to change others.

On your 291, a ‘farm’ saw, you have a ‘spur’ sprocket, which is part of the clutch cup. The 261 is a ‘pro’ saw with a ‘rim’ sprocket, that most users prefer. The pitch of the sprocket (either style) must match the pitch of the chain.

In the US, STIHL sells these saws with .325 pitch, .063 gauge chain. They don’t explain themselves. Dozens of threads discussing 3/8 pitch chains on these saws.

Philbert
 

HappyHomeowner

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Thanks everyone for all the advice. I'm sorry to ask such a simple question; I think I got a little lulled into "not thinking as much as usual" here because I basically just purchased a saw from a dealer and asked right away about swapping the saw's bar and chain and assumed all the stuff that goes with that would, well, go with that. Arrgghh. Thank goodness I really read through the manual and paused a moment before I fired it up!

Anyway, since I've started this sadly remedial thread I have learned a lot including that my dealer does in fact have in stock a 3/8 7T rim sprocket and I am going to go in today to get that swapped to match the bar and chain. They are super happy to help so no worries with that. I don't really understand why this wasn't done during the initial swapping of stuff except that the guys who helped were actually "parts" and not "service" so maybe they just didn't put 2 & 2 together?

Even when I read the manual and then looked at the sprocket that clearly says ".325" on it, I wondered whether going from 81 cutters to 72 cutters somehow made the .325 ok as in some sort of gear ratio adjustment or something. I thought to myself, "you are overly overthinking things again, just fire it up!" Thank goodness I didn't do that and thank goodness that I asked you all here first even though I admit I am feeling foolish for asking such a simple question. I feel stupid but not nearly as stupid as I probably would have if I indeed hurt the saw by using it with the wrong parts! DOH.

Please accept my apologies while I ask one more overly simple question ... the rim has nothing to do with the gauge of the bar or chain right? In other words my bar and chain are .050, does the rim need to match that as well as the pitch? I can't seem to find anything referencing specific gauges with specific rim sprockets.

Thanks again for all the help and sorry again for such simple questions.
 

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I bought two MS261C-M saws. Both with 20" bars. One with 3/8" and the other with .325". Since sold one of them and the one I have I can switch back and forth from 3/8" or .325" chains. I just switch sprocket, bar and chain as a set. This allows me to choose what to use for what situation and wood I'm cutting.

The 3/8" bar is a yellow and .325" bar is green. With 3/8" setup run full skip RSF or RMF chain. I had to buy a 100' roll to make RMF for my different length bars.

Here some images I took a couple of years ago showing the two different setups.
.
20200115_123718_resized_1.jpg 20200214_133435_resized_1.jpg 20200214_133456_resized_1.jpg 20200214_133751_resized_1.jpg 20200214_133825_resized_1.jpg 20200214_135301_resized_1.jpg
 

irhunter

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Anyway, since I've started this sadly remedial thread I have learned a lot including that my dealer does in fact have in stock a 3/8 7T rim sprocket and I am going to go in today to get that swapped to match the bar and chain. They are super happy to help so no worries with that. I don't really understand why this wasn't done during the initial swapping of stuff except that the guys who helped were actually "parts" and not "service" so maybe they just didn't put 2 & 2 together?

To confirm: the dealer sold you a 261 with a 3/8" bar, and 3/8" chain, and the .325" sprocket?
 

HappyHomeowner

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To confirm: the dealer sold you a 261 with a 3/8" bar, and 3/8" chain, and the .325" sprocket?
Correct. The saw originally was equipped with a 20" bar and chain and sprocket that had 81 cutters, .063 gauge and .325 pitch all from the factory. We knew this prior to purchasing but I just asked them if they could change things so I could continue using the chains that I have always used on my MS291. They said no problem and put an actually better bar on it (the Rollomatic ES) with the right gauge and pitch to match the chains that I already had (3/8, .050). They actually refunded a little off of the purchase price because they "took back" the original unused bar and original unused chain and only added the new type bar. They did not however change the sprocket to match the bar and I accidentally found that out truly only from reading the manual thoroughly (which I admit I don't always do). Anyway, I'm on my way now to go get their last 3/8 7T rim sprocket and should be GTG then.

So just out of curiousity, what would have happened if I fired it up and ran it with the wrong sprocket? Thanks again for all the help.
 
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Correct. The saw originally was equipped with a 20" bar and chain and sprocket that had 81 cutters, .063 gauge and .325 pitch all from the factory. We knew this prior to purchasing but I just asked them if they could change things so I could continue using the chains that I have always used on my MS291. They said no problem and put an actually better bar on it (the Rollomatic ES) with the right gauge and pitch to match the chains that I already had (3/8, .050). They actually refunded a little off of the purchase price because they "took back" the original unused bar and original unused chain and only added the new type bar. They did not however change the sprocket to match the bar and I accidentally found that out truly only from reading the manual thoroughly (which I admit I don't always do). Anyway, I'm on my way now to go get their last 3/8 7T rim sprocket and should be GTG then.

So just out of curiousity, what would have happened if I fired it up and ran it with the wrong sprocket? Thanks again for all the help.
That dealer is an idiot.
 

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I'm sorry to ask such a simple question;

That's how you learn! That's how we all learned!

So just out of curiousity, what would have happened if I fired it up and ran it with the wrong sprocket? Thanks again for all the help.
The 3/8 pitch chain would not seat correctly in the .325 pitch sprocket. You might not be able to fully mount the chain. The chain might jump off the sprocket and bar. Damage to the sprocket and chain would likely occur, along with possible damage to the side cover, bar, etc., when the chain jumped off.

Think of a bicycle, where the chain won't shift correctly to a different rear sprocket. Except, at 12,000 RPM.

Where is @Philbert when we need him and his excellent explanatory graphics?

FWIW, here is an Oregon illustration of the difference between a spur (one piece) and rim (two part) sprocket:
To switch between .325 and 3/8 pitch, the entire spur sprocket (with the clutch drum) would need to be replaced. With the rim sprocket, only the small, rim part would need to be switched.

Rim vs Spur Sprocket Oregon.png
 

HappyHomeowner

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That dealer is an idiot.

Ohh But Wait, There's More! (Sounds like some late night lousy informercial) I just got back from going back to the dealer to get the rim sprocket they set aside for me. Guess what ... it was a spur style sprocket! Then when they looked up the rim style sprocket, the regular 3/8 7T was out of stock but they had one of the 3/8 7T Picco (spelling?) and they wanted to put that on instead of just ordering the regular 3/8. They even put the picco rim sprocket on and rotated the chain manually to show that it would work well. I just told them I was very willing to wait to get the exact part and please order the exact part instead of trying to make the picco sprocket work with a non picco chain. I don't know if that was a stupid request but I just didn't want to chance things after all the other trials and tribulations. Sheesh. Anyway in about one week I will be able to finally fire up my beautiful brand new MS261 (non mtronic by the way :) ).
 

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I just told them I was very willing to wait to get the exact part and please order the exact part instead of trying to make the picco sprocket work with a non picco chain.
Good decision. 3/8 ‘Picco’ (low profile) chain has the same rivet spacing, but different drive link shapes than ‘standard’ 3/8 pitch chains. The sprockets are not compatible.

(I will look for an illustration).

Philbert
 

HappyHomeowner

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Good decision. 3/8 ‘Picco’ (low profile) chain has the same rivet spacing, but different drive link shapes than ‘standard’ 3/8 pitch chains. The sprockets are not compatible.

(I will look for an illustration).

Philbert


Aye Aye Aye! Now check this out too ... I just got a response back from Stihl from a question I posted to their technical team. I can't tell if they are just giving me disclaimer type talk or not but they're basically saying the bar the dealer picked out to go together on my 261 is possibly incompatible! What the heck! I wish there were easy to access and easy to understand schematics that show all this and be available to the public from Stihl; most of the time nowadays by the time I call an auto dealership to get the part I need I already know the number to include revisions numbers and revision of revision numbers etc. Anyway, here is Stihl's official response to my technical question:

"""""Thank you for contacting us at STIHL Customer Service.

Regarding your inquiry, we would like to clarify that the PN you provided is for a guide bar that is suitable for STIHL Series 400 saws and above, and that using any guide bar and chain combination, other the ones specified by the manufacturer, may put the performance and longevity of your MS 261 at risk as using chains and guide bars specific models were not designed for will damage the sprocket and may have unpredictable behavior.

There are several options for chain/guide bar combinations for said model, but mixing Pitch is ill-advised.

That being said, it is your device, and you may do as you please, bearing in mind it may jeopardize your warranty and the efficiency of your device.

If you should happen to have any additional inquiries, please do not hesitate to reach out to STIHL Customer Service, as we always remain at your disposal."""""

Any thought about this? Thanks.
 

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Good decision. 3/8 ‘Picco’ (low profile) chain has the same rivet spacing, but different drive link shapes than ‘standard’ 3/8 pitch chains. The sprockets are not compatible.

(I will look for an illustration).
I first snagged some clean photos from the Internet, but they did not look right. So I grabbed a few chains from 'stock (different brands, etc.). In each case you can clearly see that, even though the rivets align ('pitch' = 3 rivets / 2), the cutters definitely show the 'low profile' and that the drive links are a different shape. For all practical purposes, they are 'a different pitch'.

3:8 Std vs Low Pro.png

I just got a response back from Stihl from a question I posted to their technical team. I can't tell if they are just giving me disclaimer type talk or not but they're basically saying the bar the dealer picked out to go together on my 261 is possibly incompatible!
Yes, it is very difficult to get a straight, clear answer from STIHL, especially if you are asking about something outside of their standard specifications. Since they generally recommend a 16", .325 bar and chain, they are essentially saying 'you are on your own' from a liability standpoint.

The older STIHL Saw Chain Selection sheet (attached) clearly shows your saw's predecessor (MS260) with a 3/8 pitch, 20 inch bar.

Philbert
 

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PV Hiker

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You are lucky in a way that most Stihl dealers will sell you the saw as it comes. Then it is up to you if you want to buy other bars, chains and rim sprockets to change it to your way.

Your dealer was willing to make these changes for you but did not fully understand what parts were needed to complete the switch. They seem to be willing to order the correct part for you in a timely manner so soon you'll have your saw the way you wanted.

And a bonus is you learned a whole lot about your new MS261
 
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