What size socket to remove nut on MS261 baffle?

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Henry E

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I bought a Stihl MS261 from the prior owner who swapped the carb with a Chinese one. He said it was idling rough. He didn't want to clean it and could get a Chinese carb for just a little more then a carb repair kit.

The unit starts with the choke on. When removing the choke it goes to high revs. My limited experience tells me it is an air leak. I want to pull the Chinese carb and put back on the cleaned original. If I don't find anything obviously wrong, I will do a pressure/vac test. I will need the carb off for that also.

I need to remove the (1141 121 6900) Baffle. IPL indicates the nut is (9216 261 0700) Hexagon nut M5.

I have tried a 5, 5.5, 6. 7 and before I start reducing the outside diameter of the 8 mm in my new socket set, I was hoping to get confirmation that the socket I need to use is 8 mm.

Does anyone know for sure?
 
8mm is all i have ever had to use on stihl.
but i do not have proof for you 261

8mm will not fit down the throat to the nut. So I would need to run down the OD of the socket quite a bit. This is not a overly large OD on this socket. So it just doesn't seem right, or Stihl has a special tool to do this.

I am sure the current Chinese carb is not a correct fit. You can see a noticeable gap side to side with the bracket.
 

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It is M8 I couldn’t get my T handle 8mm down it without really pushing. I ended up going out and buying one of those cheap screwdriver handled M8 drivers and thinning the wall on the socket end. I figured if need it for all of the newer smaller saws anyway it was worth it. Next I’ll probably just buy another T M8 but for all the harder you needed to tighten them the original redneck tool may work.


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Yep. It is 8 mm. I chucked up my socket in a drill press and thinned it down some. I got the carb changed out. She starts now and idles. BUT she smokes out the clutch drum. Looks like new seals and probably new bearings. Do I need to split the cases to change the clutch side bearings?
 
Yep. It is 8 mm. I chucked up my socket in a drill press and thinned it down some. I got the carb changed out. She starts now and idles. BUT she smokes out the clutch drum. Looks like new seals and probably new bearings. Do I need to split the cases to change the clutch side bearings?

Was it used when you got it? I’d check clutch side bearing mine was used and didn’t look like many hours in it and it needed clutch side bearing. I ended up just doing both and both seals obviously.


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I had to do the same trick to get an 8mm to fit down the hole.

I found a new OEM carb on Ebay for $15, but the needles are Allen head. Otherwise very functional.

I can't think of a saw that has bearings that come out without splitting the case or clamshell. I haven't done bearings on my 261 but it didn't look like they would come out the outside of the case when I rebuilt the clutch and oiler. Are you sure they have play?
 
I had a MS261 once, bad Oiler, no spark, wouldn’t start, when removing the oil pump, I found the seal and bearing to be bad. I think those 261s are known for bad bearings. Mine also had a cracked piston on the intake side, so I would check that too.


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Looks like the safe thing to do is pull it down and check pretty much everything. Then order parts.

Anything else I should check? or change while I am in there?
If the Stihl bearings/seals are problematic, any suggestion on aftermarket parts?
 
Probably known to be problematic on the bearings due to them having really good power and guys try to push them too hard.


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I had the day off and with the rain, I got to working on the MS261. It looks like the problem was a clutch that was packed tight with sawdust.

The saw came to me with a Chinese carb on it and the original in a box. With the Chinese carb, as soon as I started the engine and took off choke, the engine raced to full throttle. The throttle movement was fine in the linkages and carb itself. I thought it had an air leak. I hoped it was the carb, but the 026, ms26x have a habit of the main bearing on the clutch side having a worn out seal. At least that is what the Internet says. This site seems to be one of the best for saws.

I cleaned the old carb (it was pretty clean), removed the high speed limiter, installed carb and set the needles to the defaults.
The saw started up fine, but smoked. It bogged pretty bad with throttle. Sounded like the chain brake was on, but it wasn't. Hoped it was a simple carb adjustment.
Smoke was coming out of the chain/clutch cover. Pulled the cover
Discovered the smoke was coming out of the clutch.

The clutch has a broken spring and one of the three shoe retainers was broken.
I pulled the clutch bell and discovered that under it was totally packed with sawdust. It appears the clutch was dragging and overheating and smoking as the oily sawdust heated up. I took almost a cup of sawdust out. She started up good. Idled once I set the LA and throttled up clean.

Put some soapy water on the bearing seal and got no bubbling or erratic idling. So I think the original carb was fine.

I think the original carb was having problems because the load on the engine while idling was inconsistent. I think the Chinese carb was a little too long, I could see that the gap in the brackets in front and behind the carb were tilting to one side. I think that created an air leak. If so, the carb may be fine for some other saw.

So it looks like I need a new
1121 160 2051 Clutch
9512 933 2260 Needle cage 10x13x10
and probably the fuel, oil, impulse lines and manifold.
 
Re: your original question Stihl has a 8mm T-handle socket that is for dealer use that is thinner walled than others you can buy. Found this out when my Kobalt 8mm wouldn't fit in... Shoot it was probably a 261 and went and got the T-handle out the Stihl toolbox and lo and behold...
 
Just get a 1/4" hex bit, size 8mm nut driver out of a cheap drill set or wherever. Then turn it down on your chain grinder, Dremel, bench grinder or whatever until it fits in the ridiculous baffle fastener holes. It IS an 8mm nut. I did that and keep it with my saw tools. Annoying but fast & easy-peasy.
 
Mine also seemed untunable until I rebuilt the clutch and oiler. It was always running the chain and dying when I used the chain brake. It turned out the clutch springs were limp like a slutty bra strap. New clutch and it tuned right up.

If your seals are holding pressure and vaccum then your bearings are probably good. If the crank shaft doesn't rattle up and down in the bearing I would leave it alone.

I wouldn't replace the intake manifold unless it fails a pressure/vac test or shows signs of damage.

Fuel filter, line and carb diaphragms are a good idea to replace if you don't know what fuel
went through it.

I would also be wondering how all that sawdust got under the clutch.
 
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