Stihl 026 headache

[KASH]

Pioneer Guy has a valid point you have tried every thing in your power to get the saw going but have got no where.Why continue only to be frustrated it is possible it is some thing simple that you missed and a person with less mechanical skills than you can spot it kinda like the saying you cant see the forest for the trees.
I having been repairing saws for 55 years but if I owned a modern saw with computer I would not attempt computer repairs even using the techniques of the modern day mechanic the so called technician REAL TITLE being do no trouble shooting or diagnosis but change parts till it works and bill the customer for all changed parts.
So to sum it up when I reach a point where I have exhausted my resoruces I eat my pride and let some one else do the repair or put the saw away till I tackle it later in time.
Remember this MACHINERY NEVER WINS
Kash

 

[Raatler]

I am by no means an expert, but I am a certified Stihl Parts Changer. So I'll tell my story in hopes that it might help you or someone else.
I was working on a one week old Stihl HT 56 pole pruner for a customer and for the life of me I couldn't keep this damn thing running. No Power, wouldn't rev, and died when you let go of the throttle. I sprayed starter fluid down the throat and it fired and sputtered... So it has to be a fuel issue. I ordered a new carb from Stihl and had the same results.
Thinking through the scenario I thought Air.... fuel... ignition. I had a known good carb... The engine was brand new so it passed the vacuum and pressure test with no issues. I had spark... obviously, or it would have even sputtered. So scratching my head, I remembered that years ago in one of our Stihl parts changing classes the instructor told us the hardest thing to diagnose was a coil issue. You could have a bad coil that gave spark but wouldn't keep the engine running. there's no test for it other than the spark test wire we hook up and it of course it showed I had spark. So the only thing I could do is try a known good coil.... so for giggles I "borrowed" the coil from the shops FS 56 (Same Coil as it's the same engine). It started on the first pull and purred like a kitten. Warrantied a new coil, installed it and haven't seen the pole pruner back in the shop since he picked it up.
If the new coil you ordered works, please let us know. I would really like to know what the issue is/was.
Good luck and stick with it...

Raatler

 

[Vintage Engine Repairs]

You say it has 115 psi, that’s very low compression and won’t run with that if indeed your gauge is correct.

I put this together, it may help your future diagnosis:

 

[av8or3]

I think your problem is staring right in your face. The fellow above is correct, 115psi will not run, and it won’t start either. I’ll bet you have a scored piston/cylinder. You won’t know until you look.

 

[av8or3]

I would also like to add that I believe , right up to the part where you said “chest beating” @pioneerguy600 had a genuine interest in helping you out. I wouldn’t blame him now if he told you to go pound sand.
Also, if you’re gonna work on these get the tools you need. Press/ vac tester is a good start.
Also, if indeed you are a mechanic you’ll appreciate the advise K.I.S.S.
Jim

 

[anlrolfe]

So then, what caused the low compression, scoring if that's the case?
1) straight gas
2) bad or misadjusted carb
3) vacuum leak
a) boots and gaskets
b) crank seals

 

[Dieselcamino]

You say it has 115 psi, that’s very low compression and won’t run with that if indeed your gauge is correct.

I put this together, it may help your future diagnosis:

View attachment 971010

Interesting, I read elsewhere anything over 110 should at least run.

 

[Dieselcamino]

So then, what caused the low compression, scoring if that's the case?
1) straight gas
2) bad or misadjusted carb
3) vacuum leak
a) boots and gaskets
b) crank seals

Looking into from the exhaust port and using a borescope from the intake it looks relatively clean inside, may just rings have worn themselves out of spec.

 

[Dieselcamino]

I am by no means an expert, but I am a certified Stihl Parts Changer. So I'll tell my story in hopes that it might help you or someone else.
I was working on a one week old Stihl HT 56 pole pruner for a customer and for the life of me I couldn't keep this damn thing running. No Power, wouldn't rev, and died when you let go of the throttle. I sprayed starter fluid down the throat and it fired and sputtered... So it has to be a fuel issue. I ordered a new carb from Stihl and had the same results.
Thinking through the scenario I thought Air.... fuel... ignition. I had a known good carb... The engine was brand new so it passed the vacuum and pressure test with no issues. I had spark... obviously, or it would have even sputtered. So scratching my head, I remembered that years ago in one of our Stihl parts changing classes the instructor told us the hardest thing to diagnose was a coil issue. You could have a bad coil that gave spark but wouldn't keep the engine running. there's no test for it other than the spark test wire we hook up and it of course it showed I had spark. So the only thing I could do is try a known good coil.... so for giggles I "borrowed" the coil from the shops FS 56 (Same Coil as it's the same engine). It started on the first pull and purred like a kitten. Warrantied a new coil, installed it and haven't seen the pole pruner back in the shop since he picked it up.
If the new coil you ordered works, please let us know. I would really like to know what the issue is/was.
Good luck and stick with it...

Raatler

I did install a new coil and that did get rid of my spark issues, but after learning that 115 psi is too low I think I may also be dealing with a low compression issue

 

[Old2stroke]

I'm with Pioneer600, in over 50 years of repairing chainsaws, I have never seen one that couldn't be made to run or at least determine WHY it wouldn't run and was too expensive to repair. Troubleshooting chainsaws requires a methodical approach, a thorough understanding of 2-strokes and a willingness to test and experiment.
Try to stay with it, we would all like to know what it finally took to make the beast run again.

 

[labans]

I think your problem is staring right in your face. The fellow above is correct, 115psi will not run, and it won’t start either. I’ll bet you have a scored piston/cylinder. You won’t know until you look.

Not wanting to argue but just get the facts out there, here is the information on compression directly from Stihl, USA website:

What is the minimum compression for my STIHL chainsaw?
Generally the minimum is 110 lbs. of compression. However, this will vary by model and compression readings alone are not enough to determine the condition of the engine. Compression gauges are not always accurate and different engines will provide different results.

 

[Dieselcamino]

After learning about the compression being too low (opinions vary wildly around the web) I have a jug and piston on order, this is the first engine of any sort that has close to beating me. I think at the end of the day it will be a variety of problems that needed to be corrected.

 

[RogerD]

Send it to someone that can fix it, you are evidently incapable.

you are evidently a ****

 

[labans]

Reply to Dieselcamino:
I also have the 60 years of experience with machines. Have been building all types of engines and have run into "unfixable" engines twice which means 2 in thousands. And so it does happen.
However, I have always been able to at least figure out what was unfixable and I think you can do the same.
I had a recent Partner that had very very similar issues and it turned out to be multiple electrical problems-----one problem hid another so that the diagnosis did not stick. Eventually had to unhitch all wiring except for coil properly gapped, properly grounded and electricity out to the plug.
Yet also had a Homelite 33cc that ran intermittently and was a hard starter. Replaced carb (it was old and ugly) and changed coil, plug etc. but not with good results. Compression showed to be 110. Finally pulled the jug and found a worn out old ring. Replaced the ring, honed the cylinder and now runs properly.
My experience with checking compression on these small engines is that you are only turning the engine over by hand and the load produced on the ring(s) is minimal compared to when running so that you might just not really have good enough compression to run the engine. Have you put about 10 drops of 30w oil in the cylinder, and pulled the engine over a number of times and then tried it?
Last, I recently had a customer bring in a Husky 440 with request to install new carb. Without any testing I bought new carb and installed it. Afterwards could not get the engine to run. Called customer who told me that the reason he wanted new carb was intermittent power, but it did run. I was stumped.
Went back to the original diagrams and found that the fuel lines were switched. Hard to see when assembled and really stupid mistake, but when changed back the engine blasted into life and cuts like a beast.
Oh, and I also had a 28 year old echo 33cc, worn out to the bone that had so many problems I just threw it away! But you are not there so just keep at it. Don't take offense at remarks from the moderator as his intentions are spot on even though they appear as a goad. And if you just get tired, share the saw with someone else---sometimes "fresh eyes" make all the difference!!

 

[labans]

After learning about the compression being too low (opinions vary wildly around the web) I have a jug and piston on order, this is the first engine of any sort that has close to beating me. I think at the end of the day it will be a variety of problems that needed to be corrected.

Excellent! Love the idea of a new jug and piston. I see success looming!

 

[RogerD]

I dont have time to read the whole thread but I did not see anything about properly timed spark. Spark is one thing, properly timed spark is key. Have you checked the key on the flywheel? The engine should run with 115 psi compression.

 

[Dieselcamino]

I dont have time to read the whole thread but I did not see anything about properly timed spark. Spark is one thing, properly timed spark is key. Have you checked the key on the flywheel? The engine should run with 115 psi compression.

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

 

[Dieselcamino]

Reply to Dieselcamino:
I also have the 60 years of experience with machines. Have been building all types of engines and have run into "unfixable" engines twice which means 2 in thousands. And so it does happen.
However, I have always been able to at least figure out what was unfixable and I think you can do the same.
I had a recent Partner that had very very similar issues and it turned out to be multiple electrical problems-----one problem hid another so that the diagnosis did not stick. Eventually had to unhitch all wiring except for coil properly gapped, properly grounded and electricity out to the plug.
Yet also had a Homelite 33cc that ran intermittently and was a hard starter. Replaced carb (it was old and ugly) and changed coil, plug etc. but not with good results. Compression showed to be 110. Finally pulled the jug and found a worn out old ring. Replaced the ring, honed the cylinder and now runs properly.
My experience with checking compression on these small engines is that you are only turning the engine over by hand and the load produced on the ring(s) is minimal compared to when running so that you might just not really have good enough compression to run the engine. Have you put about 10 drops of 30w oil in the cylinder, and pulled the engine over a number of times and then tried it?
Last, I recently had a customer bring in a Husky 440 with request to install new carb. Without any testing I bought new carb and installed it. Afterwards could not get the engine to run. Called customer who told me that the reason he wanted new carb was intermittent power, but it did run. I was stumped.
Went back to the original diagrams and found that the fuel lines were switched. Hard to see when assembled and really stupid mistake, but when changed back the engine blasted into life and cuts like a beast.
Oh, and I also had a 28 year old echo 33cc, worn out to the bone that had so many problems I just threw it away! But you are not there so just keep at it. Don't take offense at remarks from the moderator as his intentions are spot on even though they appear as a goad. And if you just get tired, share the saw with someone else---sometimes "fresh eyes" make all the difference!!

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

 

[av8or3]

Not if it’s scored. I haven’t read where he’s looked at the piston/cyl yet.

 

[Dieselcamino]

Not if it’s scored. I haven’t read where he’s looked at the piston/cyl yet.

Haven't pulled the cyl. Off but inspected it from the exhaust port and with a borescope from the intake. Looks clean but not saying it couldn't be worn out of spec.