Stihl 026 PRO

[panorain]

Hi, I have a Stihl 026 PRO saw bought new by myself. I am looking for a service manual and a parts list if possible (I have the user manual). These are important as my starting point. The saw died on me suddenly during a cut when running well. The saw has spark and fuel and 130 PSI of compression when pulled over 3 times. The saw will not start so I am thinking that there is a possible piston/ring issue. I believe I should pull off the head next.

 

-Greatest Hopes

[spudulike]

What is the compression if you keep pulling it over as 130 is a bit low. 150+ is normal on these machines with 175 being pretty good.

Have you popped off the muffler front and taken a look at the piston? When a machine dies like this, electrical or seizure are the common issues.

[spudulike]

024, 026, MS240, MS260.pdf 024 026.pdf

[panorain]

I thank you for your reply to my message, I did not see a comment in my email. Compression was low at 90 psi, pulling over multiple times. I removed the muffler front. I saw scuffing and some lines on the piston. Then I proceeded to remove the head. The piston, rings and head had *failed*. The Stihl dealer wanted 248.00 U.S.D for a head kit. I bought this kit >

Big Bore Cylinder Piston Kit For Stihl 026 MS260 026PRO Chainsaw 44.7mm -Nikasil

WWW.EBAY.COM

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Feature: Nikasil Plated. 1 x Cylinder Piston Kit, 1 x Gasket Set (3pcs), 1 x Oil Seal Set (2pcs), 1 x Needle Bearing, 1 x Spark...

from ebay. I did not use the kits Crankseals or the new bearing (not as long as OEM). I did use the piston, piston pin, clips and head from the kit. I put some wd-40 on the original crank and rod bearings. It was a bit difficult to complete this but I got everything back together correctly. The saw starts and runs now.

 

1. Do I need to break the new piston in somehow?

2. What caused the failure? I always have mixed the gas correctly.

3. Recently been using Penzoil 2 stroke marine mixing oil with the saws fuel. Is this ok? I have a 2-stroke 4 wheeler I use this oil with also.

4. What other information is good that I know?

 

@spudulike, I thank you for your help with the parts manual and service manual.

Edited July 21, 2024 by panorain
Wording

[Stubby]

23 minutes ago, panorain said:

I thank you for your reply to my message, I did not see a comment in my email. Compression was low at 90 psi, pulling over multiple times. I removed the muffler front. I saw scuffing and some lines on the piston. Then I proceeded to remove the head. The piston, rings and head had *failed*. The Stihl dealer wanted 248.00 U.S.D for a head kit. I bought this kit >

Big Bore Cylinder Piston Kit For Stihl 026 MS260 026PRO Chainsaw 44.7mm -Nikasil

WWW.EBAY.COM

---

Feature: Nikasil Plated. 1 x Cylinder Piston Kit, 1 x Gasket Set (3pcs), 1 x Oil Seal Set (2pcs), 1 x Needle Bearing, 1 x Spark...

from ebay. I did not use the kits Crankseals or the new bearing (not as long as OEM). I did use the piston, piston pin, clips and head from the kit. I put some wd-40 on the original crank and rod bearings. It was a bit difficult to complete this but I got everything back together correctly. The saw starts and runs now.

 

1. Do I need to break the new piston in somehow?

2. What caused the failure? I always have mixed the gas correctly.

3. Recently been using Penzoil 2 stroke marine mixing oil with the saws fuel. Is this ok? I have a 2-stroke 4 wheeler I use this oil with also.

4. What other information is good that I know?

 

@spudulike, I thank you for your help with the parts manual and service manual.

Marine 2t oil is a no no on land based kit .  It will over heat . Also it seems you have not found the reason for the failure . If it was an air leak and you have not rectified it you will be doing this all over again . The failure could be down to you using marine 2t oil .  .

Edited July 21, 2024 by Stubby

[pleasant]

Agree with above...never use marine 2-stroke in non marine applications. Why, just why when there's a plethora of the proper stuff around?

[spudulike]

As above and running in...lots of flat out but SHORT periods so excessive heat isn't built up so small rings/ cuts but always use the saw flat out and avoid long drawn out cuts for the first couple of hours use.

[panorain]

The saw is running again after I installed the kit. I remember a bit of a nightmare with a C clip for the roller pin. After the break in period it started to run lean a bit for some reason. I was turning the highspeed carb adjustment counterclockwise, it seemed to help then not after a bit. I think I figured out that in order to make the saw run richer to turn the highspeed adjustment clockwise in very small increments and test afterwards. I'm so grateful to have it running again this past summer.😬

 

Thank you again for your comments and help. It helped make things easier.

Edited January 26 by panorain
Wording

[spudulike]

The normal settings on the H&L screw on the carb is 1 turn out on each but 1&1/4 turns out is a decent place to start and then turn the H screw in until the saw picks up well and revs well but doesn't scream at the top revs.

Glad you are making progress.

[bmp01]

On 26/01/2025 at 01:04, panorain said:

I think I figured out that in order to make the saw run richer to turn the highspeed adjustment clockwise in very small increments and test afterwards.

Nope. 
Turning the screw clockwise is ‘closing the tap’ - saw will run leaner.

 

In your other comments you said turning screw counter-clockwise helped the saw run better (for a bit) - in this case you were adding extra fuel …. It’s likely the extra fuel is helping compensate for an air leak or an issue with fuel delivery. Be cautious, find the cause for the original failure before it repeats. I know this is repeat advice, Stubby, but…..well… it’s right innit.