Potential headscratcher - Is there anything wrong with my Stihl 026?

[Jorge Ortega]

Hi all,

I have an early model Stihl 026 (with the red master control switch) that is in decent shape for it's age. I'm not the original owner and bought it second hand. I recently replaced the air filter, carb, fuel line and impulse line with new Stihl OEM parts. The saw holds pressure and vacuum on my Mityvac pump and also has 160 PSI compression when cold.

My problem is this:
The saw will run for 10-15 seconds with the L screw at 1 turn out from the seated position and then the RPM's will slowly start to come down and the saw will die. If I start it up again, it will run for much less time and then die again. I then have to repeat the cold starting procedure to get it running where it will again run for 10-15 seconds and then die...you get the picture. If I rev the saw in this state it bogs for a second but then the revs shoot up. The saw starts to run well if I turn out the L screw. 1 1/4 turns is its happy place. Since the stock spec for this saw is 1 turn out for the L, I'm stumped as to why it can't run at this position. What could be wrong with the saw (if anything) or am I over thinking it and just let it be?

P.S
I am in South Florida at sea level

 

[Biigg50]

That’s your starting point, 1 turn out, from there you adjust it till it runs properly. Don’t get hung up on it needing to be 1 turn out.


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[Jorge Ortega]

So the sticker on the saw that says 1 turn out is just a starting point?

 

[Biigg50]

Yes, often times you may even need to take the limiter off the screws in order to get more adjustment for a particular saw to run better.


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[Jorge Ortega]

Ok, thanks a lot!

 

[Biigg50]

http://tekindoor.com/miscellaneous/stihl-chainsaw-carburetor-adjustment/


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[alexcagle]

Bear in mind, you're not shooting for the "smoothest" idle.
Most all two strokes have a rumpy idle when adjusted correctly.
This allows just enough richness to transist to higher throttle positions and maintain the mixture as close as possible to the "ideal" 14 to 1 air to fuel ratio.
One way to determine if it's set correctly, and not too rich, is to blip the throttle real quick. It shouldn't dip lower than idle.

 

[Jorge Ortega]

Ok, all of this makes sense. I think I was just overthinking it in the end and was obsessed with getting it to run at 1 turn for the L.

 

[a. palmer jr.]

Make sure the fuel tank vent is working properly. If it doesn't vent your carburetor won't get enough fuel...

 

[Jorge Ortega]

Yes, it is. I tested it with vacuum using my Mityvac.

 

[drf255]

It’s normal for the model, and no I’m not joking.

It’s happens on some, but not all of them.

Happened on early 046 also. So much, that Stihl did a recall and paid dealers to grind the intake ports. @Jacob J.

There’s a small lip where the intake boot hits the port on some. Fuel puddles there, then it drips into port. Then the idle goes down and it stalls.

If you let it idle in your hands for say 15 seconds and then you hit it, I bet it bogs out and then runs fine. Also bet if you only let it idle a few seconds, everything works normally.

If you have the standard non adjustable oiler, it keeps oiling at idle. Not sure which you have, but you may not want to let it sit idling for long anyway.

You can try another carb, or try leaning out the L. Throttle response won’t be as great, but it will take longer to do the above.

If you pull the jug and boot, you can sometimes grind the lip out and reposition the boot. This may be more than you want to do.

In addition, for some unclear reason, swapping in another coil, preferable the newer types that say “HD” and “Stihl” on them can remedy the problem. It likely has to do with the advance curve of the particular coil allowing a leaner L but still giving acceptable throttle response.

I’d also make sure no one filed the crank key and that the key isn’t sheared. It can cause as well.

Sorry for the long response.