Stihl 026 porting

[Vesa Julin]

Hi there. I bought my Stihl 026 in 1997, and it has seen a lot of use. Last summer, however, it lost all compression, and I bought a cylinder kit from eBay. I got it working and completed the job, but not without issues. The saw feels like it is lacking power, and cold start is almost nonexistent. It needs a spoonful of gas straight into the carburetor to start when cold. The new cylinder likely needs porting. I'm familiar with the subject; I grew up messing with two-stroke bikes. However, reliable data is hard to find. How much should be taken off? Exhaust open and duration, blowdown, intake open and duration, etc. I'm looking for a good balance between torque and maximum power when cutting big trees.

 

[thompsoncustom]

Well if it was a OEM cylinder than this would be easy to answer but it's impossible to know how much needs cut off the base and band on a ebay/china cylinder. Also the best performance comes from flat topping the piston when they do the base/band cut. Any saving the old OEM cylinder? Would be better to save the old one if you can.

You want your exhaust as high as you can get it which is gonna be around the 104 to 106 in a OEM cylinder. The higher number is a physically lower exhaust that opens later. Widen the exhaust to .080 of the skirt width tho you can probably go more.

Blowdown is going to depend on where your exhaust ends up but if your in the 104 to 106 range the 15 degrees of blow down is what you want which means your gonna need to raise your upper transfers.

Intake needs widened to .100 of the skirt width and lowered. I would aim for 78 degrees on when the intake opens.

Advance timing by shaving .030 off the flywheel key.

squish can be set anywhere between .010 and .015

At this point whats going to be holding you back in the stock carb and filter setup.

 

[Vesa Julin]

Thank you. I haven't lost the original cylinder. I'll look at it again and compare it to the eBay cylinder. My wife already said that I should buy a new saw. I'll prove her wrong.

 

[thompsoncustom]

a well ported 026 with machine work is a great 50cc compared to there stock form. I'm assuming you have already opened up the muffler? brazing on a deflector is a great way to put a hole in the side but still have the exhaust vent away from you and the saw if I remember correctly for that saw the muffler opening should be around 125% to 150% of the exhaust port opening on the bore side.

 

[Vesa Julin]

The exhaust is still OEM. Although I've spent my life boosting the performance of two-stroke bikes, I only realized with this issue that I could do the same for a saw. There was a time when I built log frames and I modified the exhaust so that it would blow the sawdust away from the work area. Back then, visibility was the main concern, not power.

 

[thompsoncustom]

The exhaust is still OEM. Although I've spent my life boosting the performance of two-stroke bikes, I only realized with this issue that I could do the same for a saw. There was a time when I built log frames and I modified the exhaust so that it would blow the sawdust away from the work area. Back then, visibility was the main concern, not power.

cool well let me know how it turns out or if you have any other questions.

 

[Sidecarflip]

The exhaust is still OEM. Although I've spent my life boosting the performance of two-stroke bikes, I only realized with this issue that I could do the same for a saw. There was a time when I built log frames and I modified the exhaust so that it would blow the sawdust away from the work area. Back then, visibility was the main concern, not power.

2 stroke bikes usually come with an expansion chamber or at least a pseudo expansion chamber muffler, where as saws never come with an expansion chamber, consequently, the muf will be a limiting factor as they are deficient in scavenging exhaust gases. I have an 028 as well and way back when, it got used pretty hard but in the last decade and a half at least, it has lived a easy life.

I bought it new in 67 or there about as well, bought it as well as my 090 and 075 all at the same time actually and first thing I did was open up the muff and adjust the jets accordingly. For years it's lived on a steady diet of canned fuel, either Tru-Fuel or Echo Red Armor (I own a couple Echo saws that are pretty new as well).

I really did nothing other than the muff as it's always pulled a 20" bar with full tooth chipper for me without hesitation but it's gonna need crank seals this year I suspect, it's time because of age. I did replace the impulse hose and fuel hose a while ago (OEM parts, not aftermarket).

Mine runs like a scalded dog, it's an RPM saw btw and Stihl don't build them like that toady. It's 100% alloy but the top shroud and mine has the heated handle as well.

Like my 090 and 075, I'll never sell it. They all represent an era gone by for Stihl.

One nice thing about using canned gas in it is I don't get ANY carbon buildup in the exhaust parts and last time I peeked in, the piston was totally free of any damage as was the cylinder itself.

Don't buy a new Stihl, keep the 028, it's a damn good saw, Mine is designated 028 WB by the way...

 

[James Sawyer]

Before any porting you need to know your timing numbers and what the compression squish is. I suggest if you have the original cylinder I would compare it to the present AM cylinder. Also, when you replaced the cylinder, did you tune your saw.

 

[Vesa Julin]

...

Don't buy a new Stihl, keep the 028, it's a damn good saw, Mine is designated 028 WB by the way...

Don't worry. The saw was expensive in 1997 for a young man. I thought, pay once, cry once. Nowadays, Stihl parts in Europe are cheap as dirt compared to other brands. They'll have to pry it from my cold, dead hands...

Before any porting you need to know your timing numbers and what the compression squish is. I suggest if you have the original cylinder I would compare it to the present AM cylinder. Also, when you replaced the cylinder, did you tune your saw.

Yes, when I changed the cylinder, I also replaced the carburetor parts and adjusted the carburetor. The saw runs well, but it's just bad at starting when cold and the power doesn't match what I expected from a new cylinder.

 

[James Sawyer]

Have you done a leak check (vacuum and pressure)

 

[Vesa Julin]

Good warning about eBay parts. The squish was huge 0.05. I used the gasket that came with the cylinder. It's a wonder how the saw was working at all. I started to disassemble it.

 

[pioneerguy600]

Good warning about eBay parts. The squish was huge 0.05. I used the gasket that came with the cylinder. It's a wonder how the saw was working at all. I started to disassemble it.

AM cylinder kits are well known for that problem along with port timing being way off, port shapes and directive angles being terrible, the transfer tunnels being odd shaped and often smaller than OEM, little wonder why they are under powered and down on compression.

 

[James Sawyer]

Hyway from what I hear aren't too bad, but again I've heard Meteor & Hyway have issues so not sure what to believe myself. I'm in process of rebuild on MS461 but on the fence on either a hyway or meteor piston, Pop up or not. I think I can save the OEM cylinder.

 

[Mad Professor]

Don't worry. The saw was expensive in 1997 for a young man. I thought, pay once, cry once. Nowadays, Stihl parts in Europe are cheap as dirt compared to other brands. They'll have to pry it from my cold, dead hands...

Yes, when I changed the cylinder, I also replaced the carburetor parts and adjusted the carburetor. The saw runs well, but it's just bad at starting when cold and the power doesn't match what I expected from a new cylinder.

I had that problem starting with AM air filter, choke not closing, needed a shot of mix to start cold.

Check your OEM cylinder, it might be able to clean up?

 

[bwalker]

Hi there. I bought my Stihl 026 in 1997, and it has seen a lot of use. Last summer, however, it lost all compression, and I bought a cylinder kit from eBay. I got it working and completed the job, but not without issues. The saw feels like it is lacking power, and cold start is almost nonexistent. It needs a spoonful of gas straight into the carburetor to start when cold. The new cylinder likely needs porting. I'm familiar with the subject; I grew up messing with two-stroke bikes. However, reliable data is hard to find. How much should be taken off? Exhaust open and duration, blowdown, intake open and duration, etc. I'm looking for a good balance between torque and maximum power when cutting big trees.

If you were failure with it and knew what you were doing you wouldn't be asking for numbers. A guy that ports saws for a living would be a retard to give those numbers out.
The 026/260 isn't a great unit for porting, but I only figured this out after having multiple competent people port one for me.
Aftermarket cylinders are trash, but it sounds like you had a lean condition that roached your first cylinder. Rather than fix it right you slapped a new cylinder on it again and as a result it's partially seized and has lost compression.

 

[altatim]

A guy that ports saws for a living would be a retard to give those numbers out.

Just cause someone knows your timing numbers doesn't mean anything, its an art and I'm sure that anyone with sufficient skill isn't worried about losing clientele.

 

[bwalker]

Just cause someone knows your timing numbers doesn't mean anything, its an art and I'm sure that anyone with sufficient skill isn't worried about losing clientele.

Yea, it takes some skill and practice to using a porting tool, but honestly the numbers are very important and take some R&D to arrive at. Most of the art is BS anyways. Things guys do to make port work look "blingy" often don't do anything or sometimes are counter productive.
Honestly it's just dirt bag to ask for something like that for free. Sort of like going into KFC and asking for their special recipe.

 

[Vesa Julin]

If you were failure with it and knew what you were doing you wouldn't be asking for numbers.

It's good to have a starting point.

A guy that ports saws for a living would be a retard to give those numbers out.

Success does not require professionalism, nor does using this forum. What does this matter even concern you?

The 026/260 isn't a great unit for porting, but I only figured this out after having multiple competent people port one for me.

Sounds like you kept repeating mistake on choosing competent people. That could lead to a profound disappointment. There are constructive ways to deal with it. For instance, discussing it with close ones can be very helpful. Arguing with strangers on Facebook or forums rarely provides long-term relief.

it sounds like you had a lean condition that roached your first cylinder.

That's not true. You know, chainsaws are not eternal. They tend to break every 25 years or so.

as a result it's partially seized and has lost compression.

Not true either.

 

[thompsoncustom]

If you were failure with it and knew what you were doing you wouldn't be asking for numbers. A guy that ports saws for a living would be a retard to give those numbers out.
The 026/260 isn't a great unit for porting, but I only figured this out after having multiple competent people port one for me.
Aftermarket cylinders are trash, but it sounds like you had a lean condition that roached your first cylinder. Rather than fix it right you slapped a new cylinder on it again and as a result it's partially seized and has lost compression.

There's a lot more to it for peak performance than just numbers and a lot of people that port saws for a living will give you numbers. Which multiple competent people did you have port your 026/260's?

I had that problem starting with AM air filter, choke not closing, needed a shot of mix to start cold.

Check your OEM cylinder, it might be able to clean up?

You bring up a good point after porting a 026 the carb and air filter become the restriction with OEM stuff but the AM air filters are absolute garbage for this saw. I currently run a ms460 carb on my 026 with a Vstack and 45 degree K&N style larger filter but have thought about taking a AM air filter and putting my own mesh on it around 50-75 micron so I can still ran the cover and improve airflow over the stock setup.

 

[pioneerguy600]

There's a lot more to it for peak performance than just numbers and a lot of people that port saws for a living will give you numbers. Which multiple competent people did you have port your 026/260's?



You bring up a good point after porting a 026 the carb and air filter become the restriction with OEM stuff but the AM air filters are absolute garbage for this saw. I currently run a ms460 carb on my 026 with a Vstack and 45 degree K&N style larger filter but have thought about taking a AM air filter and putting my own mesh on it around 50-75 micron so I can still ran the cover and improve airflow over the stock setup.

Winter filter works great on my 026`s and have so for 20 odd years, they breathe very well but others claim they let through fine dust. Not for me but a finer mesh may be needed for areas that have drier conditions.