Stihl MS260 - acting up, air leak or other issue?

[MartDalb]

Hi everyone

Been a while since I've had to come here for help.

I have a Stihl MS260 - that runs and cuts, but I haven't been able to find a good solid setting on the carburator. The carburator is actually almost new, original walbro.

The saw is from 2011 - not overly used, and in good condition, apart from acting really weird.

It either runs fast, then slows down idle, or bogs.

So, I tried to hold the saw in various positions, up down, on the side etc. and it went up in idle when holding the saw upward.
I sprayed some brake cleaner near the side of the saw, flywheel side made the saw noticeably bog down and almost die out in idle.

So...next step.
Took the saw apart, testing for air leaks, vacuum and pressure.
Nothing, no bubbles, no lost of pressure/vacuum.
I did spin the flywheel, and clutch around to check, still no sign of air leak on either side.
Nor is the leak from the manifold or impulse hose.

So now, I have no idea what to look for next?
I did tighten the cylinder bolts, they didn't seem loose though.

Any thoughts and ideas are most welcomed!

 

[Wood Doctor]

Fuel issue. Replace the pickup body (fuel filter) first. If that doesn't solve it, you might try removing the carb and check to be sue the the strainer is not getting clogged up. Part #14:

Clogged strainers causes more problems than you can shake a stick at.

 

[MartDalb]

Fuel issue. Replace the pickup body (fuel filter) first. If that doesn't solve it, you might try removing the carb and check to be sue the the strainer is not getting clogged up. Part #14:
View attachment 1169779
Clogged strainers causes more problems than you can shake a stick at.

Now, I normally do check up on the carb.
But this time I didnt. Since the carb hasnt run for any worth while time and the fuel filter was brand new.

But...lo and behold.

In the picture I even removed a lil of the dirt clogging it up, it was completely clogged.

Crazy, the fuel filters I have been using through 5-6 years have never failed me. On any of my saws.
Back to oem Stihl filters, even though they cost a fortune over here.


I did do this just before reading your reply @Wood Doctor. But still a huge thanks for the spot on reply!!!

Note to self, never Skip steps.

 

[Wood Doctor]

Two thumbs up! It's kind of nice when you hit the head on the nail. I have run into this demon on virtually every brand of chainsaw out there. I have often wondered if the strainer causes more problems than it solves. Anyway, they do let you know when you've used the saw a lot.

 

[Sidecarflip]

Just another reason why I use canned fuel and keep it in a well sealed container.

 

[MartDalb]

Just another reason why I use canned fuel and keep it in a well sealed container.

I only use canned as well, but I have been using non oem filters, for 5 years no problems. I keep my tanks relatively clean too.

I guess quality has gone down on the filters, they are from Saegenspezi, in Germany. They have solid aftermarket parts, but I will have to start using oem stihl filters now.

 

[Sidecarflip]

Here I use Stens parts. Reasonable and lots of time are reboxed or packaged OEM.

I quit using corn squeeze gas in my saws long ago. I even use canned gas when I lay up my bikes over the winter.

 

[MartDalb]

Here I use Stens parts. Reasonable and lots of time are reboxed or packaged OEM.

I quit using corn squeeze gas in my saws long ago. I even use canned gas when I lay up my bikes over the winter.

Yep, same here, on the gas part.

We don't have Stens parts here, sadly

 

[lone wolf]

Now, I normally do check up on the carb.
But this time I didnt. Since the carb hasnt run for any worth while time and the fuel filter was brand new.

But...lo and behold.

In the picture I even removed a lil of the dirt clogging it up, it was completely clogged.

Crazy, the fuel filters I have been using through 5-6 years have never failed me. On any of my saws.
Back to oem Stihl filters, even though they cost a fortune over here.


I did do this just before reading your reply @Wood Doctor. But still a huge thanks for the spot on reply!!!

Note to self, never Skip steps.

The OEM Stihl filters that are Orange are a finer micron.

 

[MartDalb]

The OEM Stihl filters that are Orange are a finer micron.

Yeah exactly, I have one of those on my MS361 - switching to those on all Stihl saws now.

They are three times more expensive than my old "non oem" Saegenspezi, but so be it.

 

[Sidecarflip]

I rarely get anything in either my oil filters or gas filter because I make it a habit to use my ever present small paint brush and brush off the caps prior to filling. Only takes a second. One reason I don't like the Stihl 1/2 turn caps, they always get crud under them. That and they always weep for me. No more however as I sold the MS saw a while ago. All that is left are Echo's and my old 028 which has the old style caps on it.