stihl 026 problems

[mckee]

I have an 1990 stihl 026 that i grabbed last year off an old farmer, saw was in great shape for the age and ran okay. Compression was a little low but above 100, without putting a comp test on it I do not know what it currently is. It starts and runs right now with choke then continues to run with choke off. Last time I went to use the saw was to go buck up oak 10" ish diameter for firewood, the saw bogs and wont keep a high rpm. I have requested a manual in another thread but thought that I would start this as there are guys who likely have an idea about what I need to do to fix this saw. Last year when I bought the saw, it got new end of line in tank fuel filter, air filter (mesh style) and plug. Now that it is bogging I am going to grab new fuel filter and plug. Chain is sharp and bar is in decent shape. I run 91 octane gas mixed with the stihl mixing oil at 50:1. Running winter weight bar oil at -5 C. Gas is two months old and my ms461 has no problems with it milling some of the same oak in the same conditions. (same bar oil used also)

To me, this sounds like a fuel problem of some kind or I need to adjust the H and L screws. I have no real experience tuning a chainsaw and appreciate any help.

 

[SEAM]

Possibly just a carb tuning problem.
I would also check/replace the rubber parts (fuel line, impulse line). They might show cracks (causing an air leak) on a 27-years old saw.
The 026 is a nice saw to have and certainly worth fixing...

 

[Andrew9802]

Wouldn’t hurt to put a carb kit in it and clean the carb if you are comfortable with doing that.


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[pioneerguy600]

Remove the two screws holding the muffler cover on, aT27 Torx screwdriver is all you need, pop off the cover and look at the piston through the exhaust port first, scoring will be very evident and will tell if investing time or money is required.

 

[cuinrearview]

Remove the two screws holding the muffler cover on, aT27 Torx screwdriver is all you need, pop off the cover and look at the piston through the exhaust port first, scoring will be very evident and will tell if investing time or money is required.

My experience with "farmer" saws leads me to this. On an 026 it's a quick, simple check.

 

[pioneerguy600]

Any saw that had compression down around 100 lbs I would be suspect of scoring, especially when it was used /ran that way . It`s about the first thing I check these days on low comp saws, I can actually ,feel, what is going on inside any saw by slowly pulling the recoil, other senses like hearing and sight tell me just about any problem without removing any part.

 

[SteveSr]

With a saw that old the probability of an air leak somewhere (seals, impulse, intake) is pretty high. The main clue is that it continues to run with the choke on. It is pulling air from somewhere. It is not supposed to do that. At this age I usually just tear them down and replace all of the critical rubber. If the piston looks good now it won't stay that way long if you continue to run it with an air leak.

 

[Dawnsman]

With a saw that old the probability of an air leak somewhere (seals, impulse, intake) is pretty high. The main clue is that it continues to run with the choke on. It is pulling air from somewhere. It is not supposed to do that. At this age I usually just tear them down and replace all of the critical rubber. If the piston looks good now it won't stay that way long if you continue to run it with an air leak.

Ive got a brand new after market carb for am 026 20 bucks shipped if ya want it

 

[mckee]

Okay, Havent taken saw apart yet. I live an hour from the store so I will go inquire about the lines, carb kit and a plug. Go home and check for scoring as mentioned. Fingers crossed that is not the case. After that point, I will change the lines, and check back in on here. Thank you for the input so far.

 

[SteveSr]

Okay, Havent taken saw apart yet. I live an hour from the store so I will go inquire about the lines, carb kit and a plug. Go home and check for scoring as mentioned. Fingers crossed that is not the case. After that point, I will change the lines, and check back in on here. Thank you for the input so far.

*Good* photos of the piston trough the exhaust port with the muffler cover removed would be MOST helpful!

 

[pioneerguy600]

I hope its not scored but that would not be the end of the world, they are very easy to replace the P&C on and not hard to find parts for.

 

[mckee]

Hi, got a new plug and fuel line, but here is a pic with muffler cover off. (Just two screws taken out) On another note anyone have a diagram they can send me? I need the bolts that fasten the teeth on.

 

[pioneerguy600]

Hi, got a new plug and fuel line, but here is a pic with muffler cover off. (Just two screws taken out) On another note anyone have a diagram they can send me? I need the bolts that fasten the teeth on.

It doesn`t look overly bad but the pict is rather far away. Can you wiggle/move the piston rings in their land?

 

[SteveSr]

Hi, got a new plug and fuel line, but here is a pic with muffler cover off. (Just two screws taken out)

Can you get a photo showing the two rings and the edge of the piston top?

On another note anyone have a diagram they can send me? I need the bolts that fasten the teeth on.

Check your PM

 

[mckee]

Thank you very much to SteveSr. Those we come in handy so I can tell my local dealer exactly what I need.

So update with the saw. Not sure what 'land' is. Using the smallnorange handled flat head the dealer gives out. The top and lower ring did not move and piston did not feel like it has play.

Checked compression again. (Would help if i took the fitting off and the piston didnt hit the fitting. Try again. Fitting off.)
This time 3 pulls 120 psi, 6 pulls 150. Over sitting a minute. Held psi.
3 more attempts. Same results.

Plug out. Dark with oil. It is a bosch, my dealer gave me a new champion.

It is -29C outside.
In the morning, new plug. Ill try it again.

And to clearify it starts with choke and then runs with choke off idles and runs but wont keep a high rpm when going through wood. (Wont run with choke on after it has warmed up. At -29C, that takes a bit of time)

 

[fearofpavement]

Engine needs work and probably carb needs to be cleaned and diaphragms replaced. I have a saw of this age and I had a fuel line develop a crack in it. Carb rubber parts have a limited life. I just changed two diaphragms in a 65 Mustang carb today that were very similar to the ones in chainsaw carbs. Those things were hard as a rock. Car runs great now. The vertical lines on the piston shouldn't be there. I have a few 026 saws and none of mine have these scoring marks even though they're old saws. Good news is putting a piston and rings in one of these saws is quite simple and something you could easily do with some guidance.

 

[farmer steve]

i had similar issues with an 026 and it turned out the clamp on the intake boot wasn't tight. i was just getting ready to tear the saw apart to replace all the rubber when i discovered the loose clamp. good luck. great little saws. it's what all us farmers use.

 

[Brushwacker]

Your spark plug being dark at 50 to 1 gets my attention . Are you gapping it at .020 in. . To wide of a gap often will cause running issues like you described. Your coil could be malfunctioning, less likely from what I perceive a wire could be shorting out. I have had wires with a bare spot short only when the saw was tilted in a way that caused it to touch a conductor . Doesn't sound like you have a lean condition, and it has good compression.

 

[drf255]

Run the Saw without the airfilter.

Just once please.

Report back.

"Mesh style" filter. Is it aftermarket or OEM?

Notorious Saw for pulling choke flap closed. I've seen guys go as far as splitting the case when it was the air filter.

 

[pioneerguy600]

Run the Saw without the airfilter.

Just once please.

Report back.

"Mesh style" filter. Is it aftermarket or OEM?

Notorious Saw for pulling choke flap closed. I've seen guys go as far as splitting the case when it was the air filter.

They are and more so on aftermarket airfilters. Some have problems with the choke not fully closing that makes them hard to start when cold. Not the best choke setup but just what we have to work with.