Stihl ms261 piston question (burned)
- Thread starter MartDalb
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Looks like sticking rings (in their grooves) have caused compression blow-by on the piston, probably from using cheap oil? clutch looks okay, what's the condition of the crankshaft stub?
MartDalb
Addicted to ArboristSite
I haven't taken it apart yet, so can't say. But I guess I will have to.
I do know that the saw haven't seen much use, other than running hot
The rest of the saw looks near unused honestly.
Can the piston be saved, at this point? Got my grid2000+ ready!
Hard to say, but the horizontal marks on the piston are factory and indicate low run time. It looks like there are vertical marks the remind me of either bits of a bearing cage (not likely) or bits of carbon (likely) getting bounced around and eaten by the piston. Of course, they could just be an illusion created by the picture.
giver
ArboristSite Operative
Like @Tobystihl it was probably from using cheap or the wrong oil, I put new pistons in 2 372's for a guy because he used Castrol super snowmobile oil in them, ran one till it stopped and grabbed the other and did the same!
Rebuilding an MS261 M-tronic is not an easy task. Not quite a bad as an MS 441, but close. BTDT.
I did a few and I learned after the first one to take pictures. 550xp vs 261, the 550 looks more complicated under the hood but it’s easier to rebuild.
Does that red color come off the clutch and springs? Reminds me of brake dust on car rims. A concern I would have is if the previous owner wasn’t super knowledgeable about saws and possibly smoked the clutch. Almost looks like some burnt plastic on the brake cover around the clutch? Could also just be the picture is a little off. I had a guy drop a 271 off and he fried the clutch and blew up the clutch bearings. Needed a new clutch and brake band. Lots of melted plastic.
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I would switch to red armor or Amsoil Dominator and look at that piston again after 10 tanks. I bet it starts to clean up on its own.
The comment about brake dust on the clutch seems pretty close to me. I’ve seen it on some and not on others, so I don’t actually know what causes it. But I wouldn’t worry about it if the clutch works properly
The comment about brake dust on the clutch seems pretty close to me. I’ve seen it on some and not on others, so I don’t actually know what causes it. But I wouldn’t worry about it if the clutch works properly
drf255
BAD CAD
Most strato pistons get carbon on the skirt. I thinks it’s because they puke less fuel out the exhaust.
That’s just an exaggerated example of what I normally see. They don’t get the wet gray pistons on the older saws.
I’m with Kevin, run w RA and see what happens.
That’s just an exaggerated example of what I normally see. They don’t get the wet gray pistons on the older saws.
I’m with Kevin, run w RA and see what happens.
MartDalb
Addicted to ArboristSite
gotta ask, since I haven't done a rebuild on a 261 - only 260s and 026s in that family. Whats the issue with the 261s?
MartDalb
Addicted to ArboristSite
Yea, It does come off. Quite easily after some wd40. Will take clutch off later and clean it better.
It does look like it was hard pressed, but no burns into the plastic or brake band issues.
MartDalb
Addicted to ArboristSite
Sounds like a good plan to me. I don't mind taking it apart, but I'd rather just run it!
There is solid compression, though I felt a slight bump when turning the flywheel, had me worried a little.
Turned out, the ignition module was slightly touching the flywheel on turns.
Think someone might have tried to adjust or check the ignition module.... with poor results.
Yup doin the same,,,
MartDalb
Addicted to ArboristSite
Please someone explain, what makes the 261 so hard to work on?
Doing 250s 260s etc in my sleep, almost feel like taking this apart and see for myself
It’s the newer style Stihl saws with the 1 pc cover. Little different than working on the older style where the carb was mounted in the box on the handle. Once you learn the steps and quirks of each model I think they’re easier to work on than the older modelsPlease someone explain, what makes the 261 so hard to work on?
Doing 250s 260s etc in my sleep, almost feel like taking this apart and see for myself
