Stihl 026 Chainsaw hard to crank - retrofit compression relief valve?

[PStechPaul]

Got the carburetor kit today, all the way from Chino, CA, via USPS First Class mail.




Now I gotta get busy cleaning up the saw and re-assembling with new parts. Maybe I'll try to do a leak test on the crankcase, although I don't have the equipment shown in the video. I do have an old engine compression tester, and also a manifold vacuum tester somewhere.

[PStechPaul]

Got the cylinder and piston kit in the mail today. Three days! Everything looks pretty good. Seems to be cast aluminum but is a little heavier than I expected. Perhaps Chinesium?

[Jon Heron]

I assume that for a 2-cycle engine they are mostly to control air leakage Is there a simple test to determine that?

Jon

[PStechPaul]

Well, the parts have been ordered and will probably arrive by the weekend. So I can take a good look at them and compare to the old parts after I clean them. I don't know quite how to evaluate them, except by close examination and trying to fit the piston and rings into the cylinder. I don't really want to spend a great deal of time on this, but I do want to do it right. I may try one of the solvents mentioned in my previous post, but mostly I suppose I'll use something like Scotch-brite to remove the carbon. I'm not sure I want to get into replacing the shaft seals, unless there is evidence of leakage. I assume that for a 2-cycle engine they are mostly to control air leakage Is there a simple test to determine that?

[lakeside53]

The stihl gasket kit contains both the shaft seals as well as all gaskets. For what you are going you just need the cylinder base gasket.

[PStechPaul]

I may have jumped too quickly to get the cheap kits, but they should be good enough, and I'll keep the originals in case of problems. An OEM MAHLE cylinder and piston kit is about $200 and just the gaskets are about $25 for OEM. I've generally had pretty good luck with "cheap import stuff", so we'll see how this works out. I usually wind up with messed up gas powered equipment due to poor maintenance and neglect, but I hope to do better with this. That's one reason I like electric versions - simpler and low maintenance.

[lakeside53]

What Willy said ^^^

Not sure why you want a new cylinder etc. I can't see the piston, but the cylinder looks fine. The original is likely Mahle, and the one you buy will be cheap import with thin chrome internal coating.. Clean up the carbon, take of the rings and make sure here isn't carbon packed in the grooves (clean with the right tool). Check your piston also... there are two types - 44.7mm and 44, and 1.2mm and 1.5mm rings respectively.

I never used the compression release on the ms260's. Heck, I don't even us it on my 044 or MS660! Quick drop start they fire up on 3rd pull from cold, 1st when warm.

[Willy]

............................
Also when doing these you need to be very strict about cleanliness before before taking the saw apart. Dirt and debris in the crankcase can cause all manor of issues down the road including but not limited to wear on the needle bearings, main ball bearings and leaky crank seals. All of these will require a major and expensive rebuild.
...................................
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This is why I mentioned back in post #2 of this thread to clean before disassembly.
Would have been much easier to clean the engine while it was still sealed without risking risking contamination to the crankcase.
Also remember proper assembly is a little more involved than taking things apart.

[oxford]

I don't know about that specific carburetor, but many of those carbs from Zama, Walbro, etc. (complete) can be had about as cheaply as the rebuild kits.

His links looks like it is the complete carb. I agree though, those small carbs are so cheap it isn’t worth screwing around with them.

[lynnl]

I don't know about that specific carburetor, but many of those carbs from Zama, Walbro, etc. (complete) can be had about as cheaply as the rebuild kits.

[PStechPaul]

Looks like I can get a complete cylinder, piston, oil seals, etc., for only about $25. And it seems to include a compression release as well.

https://www.ebay.com/itm/362408309076

A carburetor kit is about $15:

https://www.ebay.com/itm/294453037929

https://www.ebay.com/itm/154480446197

I've placed an order for both. I guess now I need to tear it down a bit more so I can give everything a good cleaning. I can't believe these parts are available so cheaply. Hopefully they will be of decent quality. I am impressed about how easily this chainsaw comes apart.

[PStechPaul]

Got the cylinder off. Doesn't look too bad, but I guess even 1/32" or so might significantly increase compression.

[Jon Heron]

What Lakeside said.
You can also pop off the exhaust to get a look at the piston and cylinder for a quick diagnosis too.
Cheers,
Jon

[lakeside53]

Don't over-think this...

Pop of the cylinder (2 minutes)... then you can see the piston top and the interior of the cylinder. Use a long rotary wire brush and it will be clean in no time. Get new base gasket (couple $) and use an inch/lb torque wrench when putting it back together.

Don't put anything like carb cleaner into the cylinder unless it's off - you'll end up replacing crank seals and more.

Like most Stihl products of the same era, parts are available.

Personally, unless it's real bad, I'd just leave it alone and put on an Elasto-start pull handle (Stihl OEM). Run it with Stihl synthetic mix oil 50:1 and quality gas. It will clean up in no time. I've had hundreds of 026 and other saws apart... the 026 is dead simple, rock solid, and easy to work on.

[PStechPaul]

I took the saw to the local small engine guy and he said he would have to charge $30 just to properly evaluate the saw for repair, and because it is over 20 years old, it might be difficult (and expensive) to get parts, and would not be worth it. But at least he confirmed that the difficulty in cranking the saw was not normal, and might indicate a heavy build-up of carbon in the combustion chamber, probably from being run too rich. I said that when I got it, the air filter was heavily clogged, and he said that would do it. He also said that it might be possible to pour some carburetor cleaner into the cylinder and leave it there for a good while, which might loosen the carbon enough to get it out.

I think I will take it apart and remove the cylinder, which should confirm the diagnosis and allow for proper removal of the carbon, and it may also reveal other problems.

Maybe I'll try one of the solvents recommended here:
https://toolsarchive.com/best-solven...moving-carbon/

Also some discussion and testing, but for spark plugs:
https://www.physicsforums.com/thread...posits.878629/