MS260 pro convert from .325 to 3/8?

[sugarbush]

OK Brian the truth: it was 2 1/2 chains. In managing our woodlot, cutting trails, T.S.I., blowdowns, firewood, somke pulp and sawlogs, I have to cut too much dirty wood. The stumps are cut down close to ground for trails. There it is. Bars don't like dirt. And then there are the rare times the bar will get stuck in a cut. The bar is dressed and cleaned after each cutting along with the chain.
That's the real world out here in Paradise.
The mind is open :jawdrop: Suggestions ?

can't offer any suggestions, I was just curious and you satisfied that. where are you in maine? my wife is from pittsfield. I was stationed in portland about 4 decades ago. you must be in northern part of maine I would guess. ( paradise)

 

[West Texas]

I run both 3/8 and .325 on an 18" bar on my muffler modded 026. I just don't tell it what chain I'm using and it runs through this old hard dead oak like a breeze; course I use square chisel chain too.

 

[logbutcher]

Dirty Wood and Paradise

can't offer any suggestions, I was just curious and you satisfied that. where are you in maine? my wife is from pittsfield. I was stationed in portland about 4 decades ago. you must be in northern part of maine I would guess. ( paradise)

Right on target Brian . You must have been a Coastie ?
Downeast near Acadia, next to Castine (Maine Maritime Academy).
But: I've had good luck with Stihl chains and bars for 25+ years. Anything that can handle grit and dirt better ? No, not carbide !
Benn to Pittsfield lately ? It's been a warm, slow snow winter overall. Good for working the woods though. Mud now, then black flies, then mozzies. Still Paradise without DSL now or in my lifetime.

 

[sugarbush]

Right on target Brian . You must have been a Coastie ?
Downeast near Acadia, next to Castine (Maine Maritime Academy).
But: I've had good luck with Stihl chains and bars for 25+ years. Anything that can handle grit and dirt better ? No, not carbide !
Benn to Pittsfield lately ? It's been a warm, slow snow winter overall. Good for working the woods though. Mud now, then black flies, then mozzies. Still Paradise without DSL now or in my lifetime.

havn't been back there in about 15 years. if by coastie you mean coast guard, I was regular navy, two ships were stationed in portland to train reservist. some real good memories from that state. from central maine north it's a lot like minn. but i think doesn't get as cold there but more snow.

 

[SawTroll]

... but I would tell the original poster to try switching to a
8 pt. rim first, with the 26rs chain, he would like it better. ...

Good point!

The issue is mostly one of sprocket size, and not of the pitch itself.

.325x7 is smaller, and the saw seem torquier.
.325x8 and 3/8x7 are larger, and about the same size. They will produce higher initial chain speed than the .325x7, but they will also bog down easier.

 

[logbutcher]

March Maddness and Fishing

As far as the high emotion here, it is normal,
winter is almost over, and most of these guys have not bathed or been
laid in a while, and they get a little testy. Well to be honest, some of them have never done either.........

Geez Kingfish, howddya know ? No baths hereabouts --haven't done one in say ---23 years.
Now about that "laid" thing : never tried it, but did want your pro opinion on size. Ever tried the new RSC chain for sayyyyyy 16" ?
As for testy, hey look, you get one chance in life. :monkey: You know male menopause is real. Ask those two who lurk around all the sites all day popping up like ...:deadhorse: And, Downeast Springs are looooooooooong.
So how about that RSC chain ? Since I'm 3 for 3 (see Fish above), there's a couple of new chains coming to make up for those errors in life. :help:

Minnesota Brian: 15 years is too long to be out of sight of the sea. Come before all the "from aways" buy up the land.

 

[Simonizer]

I wanted to convert my 260pro from .325 / .63 to 3/8 .50
My Stihl dealer said it can't be done . . . can't I just change the bar and rim spocket?

I have a stock MS260 Pro (2005), 20" bar, 3/8 chain. This is my camping saw, it works fine with this set-up. Cheers.

 

[Patrick1903]

Thought I’d revive this thread after almost 16 years.

We have a MS260 Pro on the farm. It’s rough. I think the bearings are in bad shape given the amount of movement in the flywheel and clutch (I.e. the crankshaft that both are attached to). I believe it had been converted from .325 to a 3/8 rim sprocket. That’s what’s on there now. The issue is the chain will stop in the cut with the engine still maintaining power. I think what’s happening is the clutch drum is worn away so there’s not enought friction on it to turn the drum/sprocket&chain. There’s been a lot of wear/heat in there and there’s a lip on the inside of the drum. I called the Stihl dealer and read off the part number to try to replace the drum. He said the part didn’t come up and he really didn’t have any idea on it. 1121160 2910B

He recommended going with the standard .325 spur sprocket for replacement. I have a .325 green bar/chain I could use if I go back to .325. I suppose I could get a new chain too, more aggressive than what I could poach from another saw with that same bar. My biggest concern is throwing a lot of money at the saw when the bearings appear so bad. At some point I imagine the top end will go if air is leaking in.

The saw runs ok right now, but wondering if I run til it dies? If I want to keep running it, does converting back to .325 make sense, since I have to replace clutch drum anyway? (At least that’s what I think is wrong with it…) Perhaps it would be less hard on the worn out saw?

Im also wondering if converting it in the first place had an impact on the worn seals. It seemed like lately the chain would not pull through by hand easily, unless you really adjust the chain just so. (I’m also thinking that the sprocket gets pulled toward the nose since it’s worn out, so that could affect the chain staying in line.). Thanks as always.

 

[huskihl]

Thought I’d revive this thread after almost 16 years.

We have a MS260 Pro on the farm. It’s rough. I think the bearings are in bad shape given the amount of movement in the flywheel and clutch (I.e. the crankshaft that both are attached to). I believe it had been converted from .325 to a 3/8 rim sprocket. That’s what’s on there now. The issue is the chain will stop in the cut with the engine still maintaining power. I think what’s happening is the clutch drum is worn away so there’s not enought friction on it to turn the drum/sprocket&chain. There’s been a lot of wear/heat in there and there’s a lip on the inside of the drum. I called the Stihl dealer and read off the part number to try to replace the drum. He said the part didn’t come up and he really didn’t have any idea on it. 1121160 2910BView attachment 955066

He recommended going with the standard .325 spur sprocket for replacement. I have a .325 green bar/chain I could use if I go back to .325. I suppose I could get a new chain too, more aggressive than what I could poach from another saw with that same bar. My biggest concern is throwing a lot of money at the saw when the bearings appear so bad. At some point I imagine the top end will go if air is leaking in.

The saw runs ok right now, but wondering if I run til it dies? If I want to keep running it, does converting back to .325 make sense, since I have to replace clutch drum anyway? (At least that’s what I think is wrong with it…) Perhaps it would be less hard on the worn out saw?

Im also wondering if converting it in the first place had an impact on the worn seals. It seemed like lately the chain would not pull through by hand easily, unless you really adjust the chain just so. (I’m also thinking that the sprocket gets pulled toward the nose since it’s worn out, so that could affect the chain staying in line.). Thanks as always.

Doesn’t sound like your dealer knows what he’s talking about. You need a small spline rim for an 026, MS260 or 261, and many other models.

But if the crank bearings are sloppy I wouldn’t run it. It might be worth something as a parts saw as it is, but not if the cylinder gets scored from sucking air or from bearing pieces going through the motor

 

[Duane(Pa)]

Ohh dear...

 

[John Lyngdal]

Sounds like it's time to tear the saw down to split the case and replace the bearings. It might be worth while to just pull the cylinder and see if it has been lean burn scored. If the P&C are toast, the saw might be best used for parts.

 

[Patrick1903]

Sounds like it's time to tear the saw down to split the case and replace the bearings. It might be worth while to just pull the cylinder and see if it has been lean burn scored. If the P&C are toast, the saw might be best used for parts.

It looks like piston is scored. How bad is this? The saw runs and has power. The current issue was that the chain would stop when in the wood, with engine still revved up. But maybe Doesn’t matter and I shouldn’t try to use it given the sloppy crank and piston condition.

 

[Patrick1903]

Here’s a video showing the crank movement.
https://photos.app.goo.gl/oH5AnXG6TwY9USkB8

 

[John Lyngdal]

Those bearings are toast. I'm surprised that there is the crankcase vacuum needed to pull fuel into the carburetor, as I can't imagine the seals are functional.
It would be helpful to see the piston skirt through the exhaust port with the piston at the top of the stroke.

 

[PV Hiker]

Absolutely bearings need replace along with seals. You'll need to tear it down to inspect all other components. Could be other parts needed replaced. Flywheel looks ruff but magnetic is still pulling. Piston could have been wobbled in the cylinder, look for damage.

Friend had me look at his 20 yr old ms170 and the play in the crank is similar. Advised him to spend $185 on a new one

 

[Patrick1903]

Those bearings are toast. I'm surprised that there is the crankcase vacuum needed to pull fuel into the carburetor, as I can't imagine the seals are functional.
It would be helpful to see the piston skirt through the exhaust port with the piston at the top of the stroke.

For my understanding, what would you be looking for on the skirt?

Also, whats the consensus on the piston scoring in the pic above?

I’ll get back to the saw maybe this weekend. For my own interest I’d also like to try to brake cleaner spray test at the crank seals.

 

[PV Hiker]

If the crank has that much movement then the seals surely have been enlarged enough for air to pass by. Keep running it only gets the piston more scared further damaging the cylinder walls. Simple pressure test will show air passing by the seals.

On those I will do a pressure test but use my air compressor with the regular turned down to ~9 psi and spray soapy water at the seals and watch the bubbles grow.

 

[huskihl]

At this point it’s not even a leak. Air is just falling out

 

[irhunter]

For my understanding, what would you be looking for on the skirt?

Also, whats the consensus on the piston scoring in the pic above?

I’ll get back to the saw maybe this weekend. For my own interest I’d also like to try to brake cleaner spray test at the crank seals.

I would say now is not the time (1) for further testing, or (2) running the saw any more. Just pull the cylinder and see if she'll buff out.

Then, you can decide to rebuild or sell it.

Roy

 

[Kneejerk Bombas]

I wonder if the crankshaft is junk. With that much movement and air entering I gotta think the lower connecting rod bearings are just as loose.
If the labor is free, he might be able to get the needed parts and put it back together for about what it's worth as a used saw. I'm not up on the used saw market but maybe a couple hundred buck for an old used 260?

As to the chain size question, a guy can put a 3 foot bar on that saw and pull 3/8 chain, but it's not going to cut very fast. I have found that in general thin kerf chains cut faster on smaller saws.