What size 026 piston is this? No marking

[beatsdealer2]

I want to order a new Meteor piston for my Stihl 026 but am not sure which size (A, B, AB) would be ideal. I can't find any markings on either the cylinder or the piston. Both are original Stihl / Mahle.

Here's an image of the piston:



Now which one should I order?

 

[drf255]

You’ll have to measure with a Mic or caliper to know.

Order an AB. Covers 95% of all jugs.

I’ve held hundreds of 026 jugs in my hands and never saw anything but A or B.

If you show me pics of both sides of the jug, I can tell you the bore.

If it’s an original 026 it’s 44mm. The MS260 started life as a 44mm (handle will specify 49cc) and ended with a 44.7mm bore (50cc).

 

[beatsdealer2]

It's definitely an original 026 44 mm. But I couldn't find any useful information on the jug except for 'Stihl BR' and 'Mahle 1121' and some random numbers on it. I can post some pictures later.

 

[Blueduce]

Clean the top of the piston, you’ll see numbers like eg. 695 that’s June 1995. You can date the assembly of that saw.
If it’s the original factory piston.

 

[beatsdealer2]

Here are some images of the jug:

 

[Mad Professor]

? All my older stihls are stamped on top of piston and jug. I'll have a look at my 026s, but they are at another place now.

Get a good set of Mics and measure both.

Replacement stihl pistons were mostly sold as A/B , a compromise for A and B cylinders.

 

[beatsdealer2]

With my trusty Mitutoyo caliper I measure the old piston somewhere between 44,65 and 44,70. Did someone install a late 260 kit on this thing? I bought it used but this seems weird.

 

[Blueduce]

If I may ask, why did you take it apart, and dose it have a red choke/off switch...?
It appears to be a January of 08, piston so if you’re sure it’s a 026 you have a rebuilt saw w/ OEM piston and cylinder.
If the cylinder is clean, then a new 260 meteor piston w/ caber rings and you’re good to go...

 

[beatsdealer2]

The saw was leaking air from the crank seals and cylinder gasket so I had to take it apart anyway. Was still running decent, though. The old piston has some minor scoring and pretty worn rings so I thought I'd treat the saw to a new one while I replace the seals and gasket.

 

[drf255]

99% sure that’s a 44.7mm 260 jug.

The non machined pad and the casted letters on the tunnels and stepped base give that away. Only later 026 pro’s had a decomp also.

The pad below is always machined on the 026, it can be left as cast on the 44.7 jugs.



44.7 pistons are available oem on the cheap on eBay. I believe it’s because there was a glut of them and not many 44.7,, 260’s made.

Your saw should have a heat deflector between the jug and the muff if done correctly. All 44.7 did from factory.

 

[drf255]

Below left is 44.7 and right 44

 

[beatsdealer2]

Interesting. I don't have the heat deflector. The saw is a late 1980's 026 except for the piston and cylinder obviously. It doesn't even have the hole for the decomp in the top cover. Could very well be it suffered a major failure in the 2000's and was rebuild with OEM parts.

So do these 44.7 mm jugs not have the A/B designation? What size piston should I buy?

 

[drf255]

44.7 oem off ebay.

Just make sure u fix reason original piston failed.

 

[Mad Professor]

What he ^ said.

I quick search of ebay shows NOS OEM 44.7 mm stihl pistons for $50, shipped.

They are stamped AB so should be O.K. on P/C clearance. I would check that anyway.

The stihl gasket kit comes with seals. Might be a good idea to pick up a heat deflector for muffler when you do the work.

If you have time would be a good time to set squish and do a muffler mod.

Do you have the adjustable carb? With both Hi and Lo screws.

 

[beatsdealer2]

Shipping to Germany is a PITA with these original pistons on eBay, though. Here they will set you back at least $100. So I will go with a Meteor AB one which I can get here for $25 including shipping and a set of caber rings.

I'll order the heat deflector and the longer screws for the muffler, even though I had no heat issues without the the deflector.

I opened up the muffler already, gave me a nice little upgrade in low end grunt but my mod turned out to be a bit noisy. I drilled a few 1/2 inch holes in the baffle and two more in the back of the can.

Carb is fully adjustable but I'm a bit scared about messing with the base gasket for squish tuning.

 

[drf255]

The heat shield isn’t necessary, especially since you opened the muffler.

 

[beatsdealer2]

So today I changed the crank seals.

Unfortunately, from all the flipping the saw from one side to the other with the cylinder pulled some gunk got into the crank case. Now the bearings feel a bit grabby when I spin the crank by hand.

Is there an effective way to clean the crank case and bearings without splitting the case? Maybe flood it with gas?

 

[Mad Professor]

So today I changed the crank seals.

Unfortunately, from all the flipping the saw from one side to the other with the cylinder pulled some gunk got into the crank case. Now the bearings feel a bit grabby when I spin the crank by hand.

Is there an effective way to clean the crank case and bearings without splitting the case? Maybe flood it with gas?

Clean every thing, BEFORE apart. You might be able to wash out with mix.

here is a 038S BEFORE I pulled cyl

P.S. It was a FILTHY FREE SAW









i

 

[Mad Professor]

The heat shield isn’t necessary, especially since you opened the muffler.

It won"t hurt.

 

[beatsdealer2]

Washing out with mix worked great. Saw is running fine with the new Meteor piston and Caber rings. Don't feel much of an improvement, though. Will power/torque improve after a few tanks with the new piston rings or is this everything I'll ever get?

Ran half a tank today cutting cookies and am a bit underwhelmed compared to my rebuilt 036. That thing goes like crazy. Has anyone run these saws side by side and can comment on their performance? I run both with 15" bars, same chain, 7 pin sprocket and the 036 easily feels twice as fast.

Will receive compression tester next week so I can post their numbers as well.