261 with a smelly surprise inside - help

[Be Stihl]

Well I was breaking down my saw for a good cleaning before cutting season. Removed the muffler and smelled stink bug! Took out the plug and sure enough he was in there squished, maybe a piece of his head is in the transfer. Just may be several down in the crankcase.
I also noticed the cylinder looks like crap. Piston looks great and has more compression than any of my two strokes, so. What to do next? I think I know the right answer but need to hear it from some with more experience than me.
Obviously the saw hasn’t ran since he entered cause he looks clean. But last year I may have had the same condition?? Just curious as to why the cylinder looks rough and dry...

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[RED-85-Z51]

The bug im not worried about but man that piston looks a bit rough. Id hit it with some oil at minimum. What oil do you mix with?

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[toadman]

this is why I leave my spark screens in contrary to what everyone says, after I found a massive mud dobber nest filling the cylinder on my 460 one year, it had sat in the garage for less than a month... Couldn't pull it over, and had to dissassemble it to fix that, lol.

 

[Ittybittyfitty]

Looks like the 50:1 bug ratio is a bit lean. For real though, what oil do you use and at what ratio?

 

[Be Stihl]

The bug im not worried about but man that piston looks a bit rough. Id hit it with some oil at minimum. What oil do you mix with?

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I use Stihl Ultra. I think the piston looks excellent. Pics are hard to see, first two are cylinder and last two shiny ones are piston.
There is a lot of carbon build up on top of piston not pictured. I can see oil running off piston but cylinder looks dry


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[Be Stihl]

this is why I leave my spark screens in contrary to what everyone says, after I found a massive mud dobber nest filling the cylinder on my 460 one year, it had sat in the garage for less than a month... Couldn't pull it over, and had to dissassemble it to fix that, lol.

I knew that would come back to bite me


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[Be Stihl]

50:1 mix on 93 non ethanol. So should I pull the cylinder? That makes me a little nervous, I have no means to pressure or vacuum test.


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[RED-85-Z51]

Thats the intake side of the cylinder? Hows your air filter look? Any signs of dirt in the intake?

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[toadman]

Have you been cutting at less than full throttle a bit? I've seen similar build up & carbon in saws where that's the case.

 

[Be Stihl]

Thanks for these replies!
Yes intake side of cylinder through exhaust. Carb and under filter spotless.
Also yes I cut quite a few white oak branches at half throttle because the saw would blast out the bottom so fast it made me nervous. It quit on me that day but has ran good since.


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[cuinrearview]

Chainsaw carbs don't have a fuel circuit for part throttle. Continued use like that can cause issues.

 

[Be Stihl]

Chainsaw carbs don't have a fuel circuit for part throttle. Continued use like that can cause issues.

Wide open from now on, thanks. Will this carbon burn off with some hard use, or should I clean it off manually?


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[arto_wa]

I don't see enough carbon in your photos to be worried about!

Which surface is the one with all scratches & how did they get there - that's not the cylinder wall I hope?

 

[cuinrearview]

Wide open from now on, thanks. Will this carbon burn off with some hard use, or should I clean it off manually?


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You may be able to find an oil that could clean some of that carbon up, but I can't reccommend anything. I would be tempted to pull the carb though and have a look at the piston on the intake side.

 

[Be Stihl]

I don't see enough carbon in your photos to be worried about!

Which surface is the one with all scratches & how did they get there - that's not the cylinder wall I hope?

That first picture that looks bad to me is the cylinder wall on intake side.
@cuinrearview I will pull the cylinder and report back with some better photos.


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[Allar]

this is why I leave my spark screens in contrary to what everyone says, after I found a massive mud dobber nest filling the cylinder on my 460 one year, it had sat in the garage for less than a month... Couldn't pull it over, and had to dissassemble it to fix that, lol.

That is a good point, never thought about it like that.

 

[TBS]

Looking at all of that carbon smearing on the intake side it'd be a good idea to look at the intake side of the piston.

 

[TheTone]

Well I was breaking down my saw for a good cleaning before cutting season. Removed the muffler and smelled stink bug! Took out the plug and sure enough he was in there squished, maybe a piece of his head is in the transfer. Just may be several down in the crankcase.
I also noticed the cylinder looks like crap. Piston looks great and has more compression than any of my two strokes, so. What to do next? I think I know the right answer but need to hear it from some with more experience than me.
Obviously the saw hasn’t ran since he entered cause he looks clean. But last year I may have had the same condition?? Just curious as to why the cylinder looks rough and dry...

There must be some attraction to chainsaw cylinders. Two of these guys crawled out of the exhaust port when I disassembled a very dirty 026.



Found this in my four wheeler snorkel. It was having fuel/air starvation symptoms. Put a screen over the intake when reassembled.



There's no hole too small for these mud wasps to nest in:



When you have a problem diagnosing some symptom on a machine that's been left outside or in a shed, always consider bug nests.

 

[Be Stihl]

Thanks again for the replies guys. I think I may have over reacted. I put a few drips of mix in the cylinder and cleaned the carbon on the exhaust. To my surprise the cylinder washed off clean as new. This has me thinking I should look into some different oil. Here is a not so good pic of what I see now.

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[RED-85-Z51]

That looks alot closer to what id want to see

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