Stihl 026 headache

[RogerD]

Yes I've had the flywheel off when I did crank seals. Shaft and keyway looked good, also checked the part # on the wheel itself

that leaves the coil if you havent tried that yet. It looks to be a very common ignition coil so you should be able to see if someone will loan you one for testing. 0000-400-1300 is the Stihl #, there are plenty of aftermarket available as well. Good luck.

 

[PV Hiker]

@Dieselcamino
First issue is that you got a FREE chainsaw, that in it’s self is a big unknown. You have now a chainsaw with unknown history as how it got to what it is.

You have first posted for help 45 days ago and there has been wonderful advice given along the way.

Your short answer replies as how you looked at something might be different than what a seasoned with experience person would look at and see situations differently. By all means not saying you did not do it accurately, just that we have no way of knowing.

Providing pictures really is a great tool to help show your story and allows more eyes to pick up possible problems.

Tom at @Vintage Engine Repairs has posted two good videos on pressure/Vacuum testing and carb repairs. Review them if you are unsure if you did it correctly.

When you did the pressure/vacuum testing did you follow the procedure Tom provided? We don’t know if you may have misses a step so we just assume you did it correctly.

Looking at the piston with the muffler off what does the face of the piston look like? What does the face of the intake side of the piston look like? We have no pictures to help you confirm if this where some of the problems might lie.

Having a bore scope is great, wish I had one, is good to look at the top of the cylinder from the muffler side and the bottom end from the intake side.

Compression testing. There are many different models and styles of these out there but for 2 stroke motors you need to be carful not to use ones for 4 stroke engines like for cars and such. We assume you know that and have ordered the correct one and basing your assumption that it is a correct value.

Electrical 026 is a old chainsaw, so the wires are old, switches that wear or even have wires the leak to ground. Inspection with removal for wear. Using a ohm meter move the wires around for those. Those 026 grounding switches for turning the motor on and off can be finicky.

You need to put yourself in the people that is helping you and by having pictures and confirming the method that was used goes a long way checking those boxes off and moving forward to other flawed components. I’m not there with you to go through all the check boxes.

You need air flow in and out, proper fuel, compression and spark at the proper time. Currently you seem to missing some of those components. Remember if you have it all correct but have too much fuel, it’s not going to run or run properly.

Wish you the best of luck it has been a long haul for you. I can tell you are frustrated. Sometimes we get so involved with something we can not see the issue at hand. Consider going back to basics a second time and maybe providing some images.

 

[RogerD]

also, dont forget to check your muffler for flow. the spark arrestor screens can get clogged up so bad there is no flow

 

[Pat Burton]

I'm at a loss, great spark, good compression, multiple carbs. Pressure/vac tested twice perfectly. Every hose/line inspected or replaced. Won't run at all now. I would give it away but don't want anyone else to have to deal with this thing.

I had same issue on a 018. Plugged spark arrestor. Has your flywheel turned a bit due to key shearing? Would still give spark and compression.

 

[Oletrapper]

I appreciate the help, I will try the oil trick this afternoon, that's a good one.

I'm putting my money on a clogged muffler. Take the muffler off and see if it will try to start. If flooded, you might have to let it dry out for awhile. jmho OT
Don't give up on us. Keep trying. And by all means, send some pics.

 

[stihltech]

Does the pulse hose pass air? The easy way to check this is remove the carburetor put a drop of thick oil or a small dab of grease on the end of the pulse hose. It sound suck it in and blow it off as the engine is cranked. Got me once. This is part of the Stihl engine check sheet.

 

[JMCK]

that leaves the coil if you havent tried that yet. It looks to be a very common ignition coil so you should be able to see if someone will loan you one for testing. 0000-400-1300 is the Stihl #, there are plenty of aftermarket available as well. Good luck.

I gave him DVOM readings from a new Ducati coil and he said it tested good.

 

[Okie]

115 compression is too low for a Stihl chainsaw. Some will run with such but some will not and they will usually flood easily, but I've seen low compression readings blamed when the comp was actually A-ok.
I had a good GM certified (Mr. Goodwrench) auto mechanic bring me his Stihl chainsaw awhile back, he said he overhauled the engine, new piston and rings due to low compression and compression was even lower with the new piston and rings. I checked with my SPECIAL chainsaw compression gauge and compression was 155, his gauge was 90. He was testing with his automotive type compression gauge.
His saw had a bad spark plug and a cracked pulse hose.
His compression gauge was not correct for a chainsaw compression therefore he got on the wrong page in his brain.

 

[Dieselcamino]

115 compression is too low for a Stihl chainsaw. Some will run with such but some will not and they will usually flood easily, but I've seen low compression readings blamed when the comp was actually A-ok.
I had a good GM certified (Mr. Goodwrench) auto mechanic bring me his Stihl chainsaw awhile back, he said he overhauled the engine, new piston and rings due to low compression and compression was even lower with the new piston and rings. I checked with my SPECIAL chainsaw compression gauge and compression was 155, his gauge was 90. He was testing with his automotive type compression gauge.
His saw had a bad spark plug and a cracked pulse hose.
His compression gauge was not correct for a chainsaw compression therefore he got on the wrong page in his brain.

Interesting, didn't know there would be a special chainsaw compression tester, I assumed PSI would be PSI

 

[Automender]

An auto compression gauge really doesn't care how long the hose is and where the check valve is because of the large displacement of the cylinder. On a small engine that displacement is small so the check valve needs to be at the sparkplug so the it doesn't increase the final compression volume. The same reason people do a base gasket delete.

 

[Okie]

Interesting, didn't know there would be a special chainsaw compression tester, I assumed PSI would be PSI

Seems strange but true.
You might review how easily a small cc engine compression gauge will not indicate correctly when testing chainsaws, weed eaters, etc. The gauges require SPECIAL schrader valves and the the valve needs to be located right at the spark plug adapter.
Lots of info on this site and on the internet about such.

Here is couple of links on this site you might review.
http://www.arboristsite.com/community/threads/compression-tester-issues.310133/
https://www.arboristsite.com/commun...mpression-gauge-and-tested-a-few-saws.348043/
You might consider taking your saw and gauge to a small engine shop that has a known correct indicating gauge and see if your gauge will read correctly when testing a chainsaw or small cc engine. Most compression gauges will read really low if they are not of the correct type/design.

 

[BrettS]

All very well saying your gauge is wrong, what about recommending which types of gauge to get?.

 

[RogerD]

After reading the two links above, I will have to call bs unless someone can convince me otherwise. The length of the hose (within reason) and location of schrader should not make a difference. Proper technique would make more of a difference. While my job is working on small engines/equipment my training was as a powersports tech.

 

[Automender]

After reading the two links above, I will have to call bs unless someone can convince me otherwise. The length of the hose (within reason) and location of schrader should not make a difference. Proper technique would make more of a difference. While my job is working on small engines/equipment my training was as a powersports tech.

If you think about it this way maybe it will make more sense. The final volume up to the squish line on a saw is imaginary 20 CCs and you get 150psi compression based on this area. Now add another 20 CCs of volume to that with a hose going to pressure gauge, You effectively doubled the volume and therefore halved the compression. If the check valve is right at the sparkplug hole you are not changing the volume because every compression stroke the hose volume fills and keeps the pressure. It will take more compression cycles to match the cylinder pressure but it will eventually get there. The automotive compression gauges that I have, have the check valve right at the gauge. As far as technique on a auto you need full open throttle but on a 2 cycle it doesn't matter since there is on valve. Air can come into the cylinder from intake or exhaust ports.

 

[labans]

If you think about it this way maybe it will make more sense. The final volume up to the squish line on a saw is imaginary 20 CCs and you get 150psi compression based on this area. Now add another 20 CCs of volume to that with a hose going to pressure gauge, You effectively doubled the volume and therefore halved the compression. If the check valve is right at the sparkplug hole you are not changing the volume because every compression stroke the hose volume fills and keeps the pressure. It will take more compression cycles to match the cylinder pressure but it will eventually get there. The automotive compression gauges that I have, have the check valve right at the gauge. As far as technique on a auto you need full open throttle but on a 2 cycle it doesn't matter since there is on valve. Air can come into the cylinder from intake or exhaust ports.

Hmmm. All this is very interesting. Can't buy the explanation about two different types of gauges. I own three types, one a direct all solid metal type that is 10" long with a schrader that is3 inches from the tip , a second one that has a rubber hose connected to a gauge and the hose is 12" long with the valve at the gauge and a third that is the same but has an all metal hose. Each gauge has a slightly different reading due to the fact that bourdon tube gauges are not perfectly accurate, but they are within a pound or so of each other. The only difference I can find when testing a two-stroke using those gauges is that when I use the gauges with the hoses I have to pull the starter rope about 6 times to be sure whereas the metal one-piece is 3 max. Otherwise the readings are the same.
If you own 3 or more different types of gauges and make a test and get wildly different readings, please let us know.
Here is some more technical info from another 'wrench.'

"To get a meaningful reading, your gauge “must” be the type that screws into the spark plug hole (with a sealing “O” ring), and it “must” have a sealing air fitting at the tip of the threaded fitting. Without these features, the readings it yields are close to useless.
In addition, it’s helpful if your screw-in type gauge has a hose-volume that is as small as possible. If your compression gauge has an unusually large hose volume, you’ll need to spin the engine through a bit faster and longer to get a valid and repeatable reading."

This has been my experience.

 

[Old2stroke]

Hmmm. All this is very interesting. Can't buy the explanation about two different types of gauges. I own three types, one a direct all solid metal type that is 10" long with a schrader that is3 inches from the tip , a second one that has a rubber hose connected to a gauge and the hose is 12" long with the valve at the gauge and a third that is the same but has an all metal hose. Each gauge has a slightly different reading due to the fact that bourdon tube gauges are not perfectly accurate, but they are within a pound or so of each other. The only difference I can find when testing a two-stroke using those gauges is that when I use the gauges with the hoses I have to pull the starter rope about 6 times to be sure whereas the metal one-piece is 3 max. Otherwise the readings are the same.
If you own 3 or more different types of gauges and make a test and get wildly different readings, please let us know.
Here is some more technical info from another 'wrench.'

"To get a meaningful reading, your gauge “must” be the type that screws into the spark plug hole (with a sealing “O” ring), and it “must” have a sealing air fitting at the tip of the threaded fitting. Without these features, the readings it yields are close to useless.
In addition, it’s helpful if your screw-in type gauge has a hose-volume that is as small as possible. If your compression gauge has an unusually large hose volume, you’ll need to spin the engine through a bit faster and longer to get a valid and repeatable reading."

This has been my experience.

It's not the type of gauge that matters, it's the location of the Schrader valve and the type of valve that's important. If you don't believe this, try measuring the compression on a 25cc trimmer with an automotive gage using a standard valve located at the gauge and an 8" hose, then do it with a gauge using the special low pressure valve located right at the spark plug hole.

 

[RogerD]

but air does not enter through the exhaust port, it enters through the transfer ports.

 

[Automender]

Hmmm. All this is very interesting. Can't buy the explanation about two different types of gauges. I own three types, one a direct all solid metal type that is 10" long with a schrader that is3 inches from the tip , a second one that has a rubber hose connected to a gauge and the hose is 12" long with the valve at the gauge and a third that is the same but has an all metal hose. Each gauge has a slightly different reading due to the fact that bourdon tube gauges are not perfectly accurate, but they are within a pound or so of each other. The only difference I can find when testing a two-stroke using those gauges is that when I use the gauges with the hoses I have to pull the starter rope about 6 times to be sure whereas the metal one-piece is 3 max. Otherwise the readings are the same.
If you own 3 or more different types of gauges and make a test and get wildly different readings, please let us know.
Here is some more technical info from another 'wrench.'

"To get a meaningful reading, your gauge “must” be the type that screws into the spark plug hole (with a sealing “O” ring), and it “must” have a sealing air fitting at the tip of the threaded fitting. Without these features, the readings it yields are close to useless.
In addition, it’s helpful if your screw-in type gauge has a hose-volume that is as small as possible. If your compression gauge has an unusually large hose volume, you’ll need to spin the engine through a bit faster and longer to get a valid and repeatable reading."

This has been my experience.

but air does not enter through the exhaust port, it enters through the transfer ports.

If there isn't a burning charge to expel as soon as the piston passes the exhaust the air pressure is the same as it was before compression and air will rush in. I least that is what I think.

 

[labans]

It's not the type of gauge that matters, it's the location of the Schrader valve and the type of valve that's important. If you don't believe this, try measuring the compression on a 25cc trimmer with an automotive gage using a standard valve located at the gauge and an 8" hose, then do it with a gauge using the special low pressure valve located right at the spark plug hole.

The above responses clearly indicated that there was a belief that there is a 'different type' of gauge needed: Brett S said..."All very well saying your gauge is wrong, what about recommending which types of gauge to get?."
If you read my post I was hoping it would be clear that I have used all 3 "types" of gauges that I own, on various 2 stroke motors. So I HAVE tried different gauges. And as I said, using the proper technique, I have not found a problem with getting a good reading from either of the three. While I appreciate that you have had problems with any gauge other than your "gauge using the special low pressure valve located right at the spark plug hole," there are other posters here that have not had any problems with their 'non-special' gauges. And I would also like to mention another problem that has come up in the past which is that there are some gauges that leak at the schrader valve, when brand new direct from the factory. It is a fact that Snap-On gauges have this problem and while it is a minuscule leak that does not cause a problem when testing a V8 or other large volume engine, it drastically affects reading on 33cc and other small engine readings. Maybe you had that leaking problem with your regular gauge but not with your "special" gauge?
Still, I think most folks here need to know that in order to get a good reading on small CC engines, it is imperative to take 2,3 or 4 readings and be sure to crank the engine vigorously while taking those readings.
I know that on small motorcycles, like 125cc and smaller, it is recommended to push the bike while in gear in order to get a good reading, as opposed to using the kick-starter.

Last, along with others, I request that you please reveal the brand name and model of the "special" gauge that you use; a photo would also be helpful.

 

[bigbadbob]

This is a great thread.
Please dont part out the saw.
Maybe send it to someone for a different opinion.
We all think different.
Or sell it as is.
I would really like to see it running and what was found.