Stihl 026 Leakage Test

[2tone]

In the 026 Service Manual Leakage Test - Pressure and Vacuum Test- it does not mention plugging the impulse line when testing. In the photos it is not plugged. Should it be?

 

[tug]

I have never used a stihl testing block as pictured. But normally eveything has to be block so you can put pressure or vacuum on the crackcase.

 

[2tone]

Thanks tug!

 

[lone wolf]

Thanks tug!

Yes it either gets plugged or you use it for the MitiVac tool or what ever you have to plug into . Everything is supposed to be tight no leaks closed area! Get some soapy water in a spay bottle to check seals and plug and cyl base gasket for leaks ,look for bubbles.

 

[2tone]

Yes it either gets plugged or you use it for the MitiVac tool or what ever you have to plug into . Everything is supposed to be tight no leaks closed area! Get some soapy water in a spay bottle to check seals and plug and cyl base gasket for leaks ,look for bubbles.

Thanks, I'll give it a try.

 

[lone wolf]

Thanks, I'll give it a try.

What tester do you have does it do vac and pressure? Bike tubes cut up make a good gasket to seal the exhaust of course you need like a metal plate.

 

[SteveSr]

In the 026 Service Manual Leakage Test - Pressure and Vacuum Test- it does not mention plugging the impulse line when testing. In the photos it is not plugged. Should it be?

Properly used the Stihl tool adapter blocks the impulse port.

 

[2tone]

I have an older Mitivac 4555 vac only. I found the duo-conversion kit on ebay and now it does pressure and vacuum. I tested it and no leak down on just the Mitivac. I made a wedge from thick rubber gasket stock. I also made a plate from thin flat bar stock using the exhaust gasket as a template. I made a cardboard template from carburetor. I was thinking of making a plate and tapping the center with a vac fitting. Maybe now will just make another rubber gasket wedge and cover plate and use impulse line to pressure/vacuum test through.

 

[tug]

They make a fitting that goes in the spark pug hole, that has an fitting. It is cheap and works well. You can make them out of a spark plug also, it is a pain. Sounds like you are well on your way either way.

 

[2tone]

Properly used the Stihl tool adapter blocks the impulse port.

Thanks SteveSr. I looked at adapter block and see what you are talking about. Wasn't in 026 Service Manual.

 

[2tone]

They make a fitting that goes in the spark pug hole, that has an fitting. It is cheap and works well. You can make them out of a spark plug also, it is a pain. Sounds like you are well on your way either way.

Thanks for the feedback. I wished the Service Manual had covered the impulse line. In the meantime I looked up the impulse line and its purpose and understand why it needs to be plugged.
Thanks. If I have any questions going forward, I'll post. Thanks again.

 

[drf255]

Thanks SteveSr. I looked at adapter block and see what you are talking about. Wasn't in 026 Service Manual.

This is true on some models, but not the 026/044/066 etc...

The Stihl oem tester is assymetric to enable blocking the impulse on models with the impulse coming through the intake boot and entering the carb through the face (like 036/038/361). On Stihl models with an impulse that enters the carb through a separate barb on the pump side, the impulse needs to be plugged as well. I use a golf Tee myself.

 

[2tone]

This is true on some models, but not the 026/044/066 etc...

The Stihl oem tester is assymetric to enable blocking the impulse on models with the impulse coming through the intake boot and entering the carb through the face (like 036/038/361). On Stihl models with an impulse that enters the carb through a separate barb on the pump side, the impulse needs to be plugged as well. I use a golf Tee myself.

Thanks. My O26 impulse line enters the carb on a separate barb on the pump side.

 

[lone wolf]

Thanks. My O26 impulse line enters the carb on a separate barb on the pump side.

When is the test ?

 

[2tone]

I sealed the carb off with a solid rubber gasket and did the pressure and vacuum test at 7.5 psi. Both pressure and vacuum tested fine. No leakdown at all.
Thanks to all for the help.

I purchase my 026 new in 1996. It has been a good saw. I bought it because the house I purchased had a very large tree down in the side yard. It did great. Another tree had to be taken down a couple of years later. A couple of years later a hurricane took a couple of trees down and then not much use until Katrina took down about 25 small to medium trees. About 7 or 8 trees in it Istarted to stop running when I sat it down then became hard to start when hot. I took it to a saw shop and they rebuilt the carburetor and it worked better but started to act the same about 3/4 the way through. I just rested it when it didn't want to restart. After that I moved with job relocation to Ohio. When I had some storm damage here I took it to the Stihl dealer and they rebuilt the carburetor and it did ok. A few years ago my neighbor had a large tree that died and needed taken down and it barely ran and not much power at WOT. I took it back to Stihl and they rebuilt the carburetor and it run ok but not great. Last year I had a small tree with storm damage and after a couple of cuts it didn't want to restart. I finished with my Kombi pole pruner. I have been using it for light work around. I want to take down a tree leaning over my workshop. I though carburetor again and purchased a rebuild kit and installed it didn't help. So I bought a new Stihl carburetor and put it on. It stated up and I cut up a dried log for camp firewood. After a couple of cuts same problem. So after searching forums I thought crankshaft seal. They test fine.
More research and I decided to test compression. 90 psi cold WOT.
I looked through the exhaust port and there are veticall lines - 1 heavy on the piston.

 

[lone wolf]

I sealed the carb off with a solid rubber gasket and did the pressure and vacuum test at 7.5 psi. Both pressure and vacuum tested fine. No leakdown at all.
Thanks to all for the help.

I purchase my 026 new in 1996. It has been a good saw. I bought it because the house I purchased had a very large tree down in the side yard. It did great. Another tree had to be taken down a couple of years later. A couple of years later a hurricane took a couple of trees down and then not much use until Katrina took down about 25 small to medium trees. About 7 or 8 trees in it Istarted to stop running when I sat it down then became hard to start when hot. I took it to a saw shop and they rebuilt the carburetor and it worked better but started to act the same about 3/4 the way through. I just rested it when it didn't want to restart. After that I moved with job relocation to Ohio. When I had some storm damage here I took it to the Stihl dealer and they rebuilt the carburetor and it did ok. A few years ago my neighbor had a large tree that died and needed taken down and it barely ran and not much power at WOT. I took it back to Stihl and they rebuilt the carburetor and it run ok but not great. Last year I had a small tree with storm damage and after a couple of cuts it didn't want to restart. I finished with my Kombi pole pruner. I have been using it for light work around. I want to take down a tree leaning over my workshop. I though carburetor again and purchased a rebuild kit and installed it didn't help. So I bought a new Stihl carburetor and put it on. It stated up and I cut up a dried log for camp firewood. After a couple of cuts same problem. So after searching forums I thought crankshaft seal. They test fine.
More research and I decided to test compression. 90 psi cold WOT.
I looked through the exhaust port and there are veticall lines - 1 heavy on the piston.View attachment 818137

That piston is bad take the cyl off and see if the cyl is usable then get what is needed not China junk but OEM parts . The reason it ran bad is the low compression which is worse when hot.

 

[2tone]

That piston is bad take the cyl off and see if the cyl is usable then get what is needed not China junk but OEM parts . The reason it ran bad is the low compression which is worse when hot.

I also picked up the saw by the pull cord without the bar, clutch, muffller, covers etc... I picked it up gently. The saw drops anywhere 18 to 24".

I'll tear it down tomorrow. Have to mow and work afternoon shift.
What would cause the piston to score? Running lean?
Also the scrench will not fit through the holes in the head. Special tool?

 

[lone wolf]

I also picked up the saw by the pull cord without the bar, clutch, muffller, covers etc... I picked it up gently. The saw drops anywhere 18 to 24".

I "ll tear it down tomorrow. Have to mow and work afternoon shift.
What would cause the piston to score? Running lean?
Also the scrench will not fit through the holes in the head. Special tool?

Lets see pics ,clear ones of the intake side of the piston and the exhaust side then I may be able to say what might have did that.

 

[2tone]

Tore the saw down. Not as good as I hoped.
The cylinder bolts on the exhaust side were snug but not tight like the intake bolts. The top of the piston was hitting the cylinder on the intake side.

 

[lone wolf]

Tore the saw down. Not as good as I hoped.
The cylinder bolts on the exhaust side were snug but not tight like the intake bolts. The top of the piston was hitting the cylinder on the intake side.

Did it have a base gasket or sealer?