The possible factory issue with 026's?

[Wood Doctor]

Neither one of my 026 PROs does this. I have to wonder if that makes a difference. Anyone know? Both of mine have operated flawlessly for five years or more. I flip a coin to see which one gets used. I simply cannot tell them apart.

 

[Adirondackstihl]

A lot of it has to do with how the low speed circuit is tuned IMO.
Proper ratio of L & LA probably won’t do it as much as a carb tuned a little on the rich side with a heavy LA adjustment.
Just an observation

 

[RI Chevy]

Good point Jeremy. [emoji106]

 

[SteveSr]

A lot of it has to do with how the low speed circuit is tuned IMO.
Proper ratio of L & LA probably won’t do it as much as a carb tuned a little on the rich side with a heavy LA adjustment.
Just an observation

I think that this may be a good part of it. Part of the symptoms is that the saw doesn't want to accelerate which makes you think it is too lean on the low end. So you richen the low end up and the stalling gets even worse. This is how the 403 carb behaved.

Based on this thread the issue is fuel pooling in the intake. So if you adjust the carb to eliminate the fuel pooling the saw won't accelerate because it is too lean. And if you set it to accelerate you get fuel pooling and the position dependent stalling. Somewhere in between the saw almost runs!

 

[RI Chevy]

It could be your filter too. There is A LOT that is dependant on air filtration. Try taking the filter off and run the saw and see the difference.
That is why the metal mesh filters always make the saw run stronger!
Just be cautious of a lean condition on the top end.

 

[countryhog]

So as to not really affect the timining can you not just notch at the cylinder wall? Course that doesnt help at the boot

 

[Adirondackstihl]

So as to not really affect the timining can you not just notch at the cylinder wall? Course that doesnt help at the boot

There’s nothing going on at the wall.

 

[countryhog]

So all the pooling is at the boot and no grinding necessary at the cylinder wall?

 

[Adirondackstihl]

So all the pooling is at the boot and no grinding necessary at the cylinder wall?

Correct

 

[countryhog]

Correct

Thanks

 

[Simondo]

Working on a 024 today and having the normal issues that the 024-026 ........often seem to have with what we believe to be "Fuel Puddling" on the cylinder side of the carb.
Well....here is what I found.
Walbro WT-194 carb, early small air filter with spit back plate ,new carb kit and a stock saw 40:1 .
To give a datum I used the Stihl basic set up . Ie...L =1 H=1 ,warm up.... then set 3600 rpm using LA.
Turn L clockwise to get max rpm , looking for 3700 max...back to using the LA and bring rpm down to 3300 rpm then using the L anticlockwise bring rpm back to 2800-3000 rpm (i went more to 3000 rpm end).
Lastly set H to give 12800-13000 max free rpm.
The result.
Ok..ish to start and as per normal I (and like you all ) started to micro adjust the L and LA to try and stop the "sit and idle for a while...pick up the saw and drop the nose ...kills the saw" issue.
I got some improvement but you just end up with "Less" of a issue and not a cure.

Here is where things changed....take the air filter off as you wont need the choke ...start the saw and see how much "spit back" the walbro has.
Now....Leave the saw to idle and then try standing it on its nose .
I had no issues with the filter removed and the back box in place. I think somehow the fuel loads up in the filter from spit back and then pops forward on the back of the butterfly thus drowning out the saw when you tip it up on its nose. To some degree the more the LA is open the less this extra fuel seems to have a effect with the filter in place...but then the idle is much to high.
See what you all find........
@Wood Doctor @drf256 @Adirondackstihl ..Ect

 

[Duane(Pa)]

Hmmm. 036 has a piece of fiberglass foam built in to the AF to trap spit back. You may be onto something.

 

[Basher]

Run a steel mesh filter.

 

[Simondo]

Run a steel mesh filter.

This 024 is pre high top and has a steel mesh filter.

 

[Basher]

I run steel mesh and I don`t have this problem on more than a dozen of these saws, 024 and 026. You can ask my cutting partners, even they run some of my 026`s.

 

[Simondo]

I run steel mesh and I don`t have this problem on more than a dozen of these saws, 024 and 026. You can ask my cutting partners, even they run some of my 026`s.

If your not having this well documented issue, can you offer up some information ?

 

[Basher]

All I do is run them tuned proper and a clean non restricted airfilter. I have not encounter any idle issues, all my saws run 194`s on them.

 

[Finnrpm]

So if you adjust the carb to eliminate the fuel pooling the saw won't accelerate because it is too lean. And if you set it to accelerate you get fuel pooling and the position dependent stalling. Somewhere in between the saw almost runs!

My rebuild 026 ( oem cylinder & meteor piston + WT-194 / plastic air filter ) went from "almost runs" to completely useless when temperatures started to go below freezing. Also spitback increased to a point that i was assuming a serious fuel leak!!
After removing the ridge from intake side and slightly trying to shape the intake more "straight", it now runs good for a firewood saw without this loading issue.
Stihl's recipe for adjusting idle, dropping idle rpm from 3300 to 2800 with L-screw does not work on my 026. It goes too rich on the low end. It needed a small search to find the sweetspot and final idle is around 2900-3000 rpm's.
Without this thread i probably would be still trying to find resolution for this german engineering puzzle.....
Thanks for the op!!
RV

 

[HP Ultra]

Thank you guys for this thread !
This issue did also occur at one of my STIHL 026' s. (Drop the nose > idle drops instantaneously 500 rpm).


According to the comments I checked the following parts by interchanging:
- different Walbro and Tillotson carburetors: no difference
- steel mesh and plastic air filter: no difference

So at last the opening of the intake was widened by grinding, such that
the ridge between manifold and intake got minimized:
Now the idle does no longer change, whether you drop the nose or not.
The acceleration is slightly better, maybe.