Stihl 026 rebuild

[Brewz]

Well........ maybe not a complete rebuild at this stage. Just a cleanup until I get some advice from the great folks on here.

Story...... bought an 026 Pro with the decomp, adjustable oil pump etc.
Cost me a couple hundred Australian $$$ posted to me.







It turned up and looked good.
Bar has been dressed with a grinder and is not something I will use. I will have a go at fixing it up.
Put some fuel in it, pulled the cord and off she went. Badly out of tune, very rich and struggling to idle cold, but it ran!
Shut it down and proceeded to strip it.
Checked compression and got 175 psi. What would one of these saws register normally?
Pulled the muffler and it was layered and clogged with carbon and oil and there is a black layer on top of the piston and lining the exhaust port. Its not thick though, just a thin film. The rest of the piston and jug looks as new!
The muffler is a no baffle unit and its got a fully adjustable carb....... Win Win!


I think I know why it wasn't running well



It was obvious while stripping it that it has never had a screw removed. Its been bought and used and that's it. Not messed with or cleaned.
The air filter has some splits in it so will need a new one.
EVERYTHING is layered with oil clogged saw dust. I have picked most of this out with a screwdriver and plan to plug the motor ports and clean it up with degreaser and compressed air.
Under all the crap it looks great though.






Once its clean the plan is to pull the jug and clean out the inside of the motor. I'm not taking it off till all the external crap is gone!
The bearings feel VERY tight and the seals look perfect and show no signs of leaking so I am thinking I may avoid splitting the case and leave the bottom end as is for now.

Next question........ is it ok to just use some clean petrol to clean out the bottom end? Thinking I might even use some old 2 stroke that has sat for a while and is mixed with an oil I have stopped using. I just want to rinse it out and make sure there are no bits in there before I put it back together. I will lightly oil the bearings before I put it back together.

For now......the only mod I plan is to make sure the jug ports are free of burs etc and do a muffler mod. Also going to fit a low restriction spark screen.
Will replace the 2 x oil lines, fuel line, impulse line and the front AV rubber bushing is stuffed. Going to order OEM parts as thus far my experience with cheap copy's is not good. They look the same but are made from inferior materials.
Carb kit, re-assemble, tune and see how it goes.

Will use if for a while before I go machining pistons flat and porting etc....... I have been reading

Now back to my earlier question on compression........ if 175 is low for these I may get some new rings.
Should I bother or should I just clean it up and crank it?
I will get some pics of the jug and piston tomorrow when I pull it apart.

Third question.... The Stihl manual I have doesn't list Idle and max revs. What should I be aiming for stock?

Cheers

 

[Brewz]

Another question:

What is the advantage of the 44.7mm "big bore" kit over the standard 44mm jug and piston?
0.7mm isn't much....... are they worth it if I was looking for a non OEM jug and piston to play with porting?

Edit: just worked it out at 1.59% bigger.
Why bother even making them?

 

[Definitive Dave]

Big bore not worth it usually on this saw, unless you have to replace it anyway for some reason.
Dave

 

[scallywag]

A couple hundred $$ posted!.....You've done well!!

 

[gritz]

Looks like you're on the right track. 175psi is great for a stock saw. I wouldn't split the crankcase. No need to. You're fine to rinse the crankcase with 2-stroke mix. I do it all the time on saws that need a new top end. I just pour it in, slosh it around, pour it out, and repeat until the fuel comes out without any discoloration or debris. Then I turn it upside down and let all the excess fuel drop/evaporate out. Just make sure to put a dab of oil and work that in before you put it all back together. I'd get new oil seals if it were me. The flywheel side WILL fail at some point. That's a cheap piece of mind IMO. What model carb does it have? Wt-22b, 194? Good luck!

 

[Brewz]

Carb...... not sure.
Cant find any numbers that line up with those?

Pics:

 

[Brewz]

would love to know exactly what carb I have

 

[Brewz]

Looking in my Stihl 026 parts manual, it looks like what they list as a WT-426 ?

 

[Brewz]

I cant find any numbers on the carb that line up with any carb variants listed for the saw?

 

[gritz]

Wt-394 is the stamping you are looking for. That's a good carb. Get yourself a walbro d10-wat or k10-wat to rebuild it. I forgot to mention, just burn that carbon off the spark screen with a handheld propane torch. Heat it up, then just blow it out with compressed air. Repeat until all the carbon is gone. Doesn't take that much heat really.

 

[Brewz]

Funny...... I cant find any reference to a WT 394 in the Stihl part manuals?

 

[gritz]

Funny...... I cant find any reference to a WT 394 in the Stihl part manuals?

It's quite possible that your carb might have been from an MS260 or something and that's why you aren't seeing it for the 026 parts diagram. I swap carbs around on all my saws a lot. There's only slight differences between the WT series carbs used on these saws. The exception would be the WT-22B carbs that actually have a smaller carb throat than the others. All the rest are pretty similar. (WT-194, -394, -426, etc.) Either way, the only things you would need for that carb come in the K10-WAT kit. I generally just use the D10-WAT kit (diaphragms only) and then get the 5-packs of metering needles separate (either 75-75-7 or 82-75-7). This saves me a lot of money over time.

 

[Brewz]

Hi Gritz
Really appreciate your help so far.
I had a look at your porting job on the 026 and am thinking I might do a similar job down the track. I want the saw to be light but powerful. I don't want 2 million RPM, just usable torque as it will be a work saw. I will pit it back together when all the new hoses I have ordered show up, and run it stock to see how it goes and get a base performance benchmark.
I have been looking at carb kits and they all list a K11-WAT kit for the 026/260 carbs? Is that different to the K10 you mentioned?
I recon the WT 394 carb has been fitted so it can use new MS260 air filters.
I checked the squish today and its at about .028 which is OK but I would like it at .020
A coke can is not thick enough so I will need to remove the stock gasket, measure the squish with no gasket and find some gasket material the thickness I need.

I got it all cleaned up today. The top of the jug and piston were lined with a thick layer of carbon. It looked like it had been starting to make carbon on carbon contact.
Cleaned it all up and it should be a lot better now. Piston and rings look good so they will go back in for now but all the oil grooves on the sides are gone so will order a new Meteor piston down the track.
Cleaned out the muffler which was lined with tar like muck, gave the front cover the mandatory mod and fitted a new spark screen.
I also filed the muffler flange face on the jug flat as it was quite uneven and causing leaks around the gasket under the muffler. I polished it up after I took the photo which looks rougher than it is.
Smoothed out the exhaust port and matched the muffler to it.

While I was in the Stihl shop ordering the replacement hoses ($80 for 4 hoses and 1 x AV mount........ they dont miss ya) I asked for a price on a replacement sprocket cover.
$180
I said....... that's almost what I paid for the entire saw?
I will get a $20 Chinese special off evilbay as the original one has a hole in it. I would have been happier with an original one but I'm not paying $180 for a bit of die cast aluminum with "STIHL" written on the side.

Pictures below:

 

[farmer steve]

post up in the trading post for the sprocket cover .i'm sure you may be able to find someone that has one. maybe even some one from down under. i have a 026 that my brother found in a ditch several years ago. never could find the owner so after that i put about $100 in it and it runs fine. it looked liked yours with all the grime. i use starting fluid and air to clean up crusty saws. good luck.

 

[Brewz]

Thats a good idea! Will do!

I used a couple cans of $2 degreaser from the local auto shop and compressed air.

 

[drf255]

JB Weld, then sand and paint the side cover.

 

[Brewz]

I pulled the jug again this arvo and decided to remove the gasket and measure the squish without it.
broke a ring pulling them off so I guess that's a good excuse for a new piston and rings.

Squish measured .009
Gasket measures .019 (0.483mm)
Thats adds up to the .028 I measured.

I am ordering some 0.25mm gasket material (0.010) which should give me a 0.019 squish.

That's with the old OEM piston...... going to fit a Meteor piston and Caber rings but it should be close to that.

 

[Stihlofadeal64]

Careful on the squish on the 026. Stihl actually makes a gasket to aid you in your quest -- 1118-029-2306 (it is a .5 mm gasket) and with a new set of rings for your piston you should make plenty of compression. If you have an itch to buy new stuff for your saw I would look at a Meteor replacement piston kit. Not sure of their availability in your area of the world though. Looks like a nice project going on.

 

[drf255]

Careful on the squish on the 026. Stihl actually makes a gasket to aid you in your quest -- 1118-029-2306 (it is a .5 mm gasket) and with a new set of rings for your piston you should make plenty of compression. If you have an itch to buy new stuff for your saw I would look at a Meteor replacement piston kit. Not sure of their availability in your area of the world though. Looks like a nice project going on.

Isn't .5mm the same as .020?

That would put him back where he started.

Brewz, they make brass shim material that comes in multipacks of different precise thicknesses. I've used it a few time for that final squish adjustment.

 

[Brewz]

Yeah the gasket I have now is the 0.5mm one
I have ordered this stuff for a gasket

http://m.ebay.com.au/itm/High-Tempe...0mm-x-240mm-x-0-25mm-/301114252015?nav=SEARCH

I also ordered a new meteor piston, clutch springs and chain bumpers for the sprocket cover.