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Starting a Stihl 026 rebuild - looking for tips

Kevin GB

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Morning all, I picked up a "Somewhat running" Stihl 026 a few weeks ago. It will start but runs poorly, pulled the muffler and the piston is scored so I am going to pull the top end to replace the piston and cylinder if necessary. Hoping to save the cylinder, but I'll see what it looks like. The piston isn't too bad so I'm hoping the cylinder isn't damaged beyond repair. I figure while it's apart I may as well replace the fuel lines and crank seals as well, check the intake, rebuild the carb. Anything else worth looking at or doing while I'm there ? I'll check the condition of the AV parts and all as well.

I've worked on mower and tractor engines for years but this will be my deepest into a chainsaw. Any tips or tricks on the 026 ? (It looks to be an older model with the Wt-194 carb and the old style air filter, no de-comp) Just looking for any advice from those that have pulled these apart before so I don't do anything silly or make something worse. I looked up the posts on cleaning up cylinders, that should be no problem. Any tips on the ring and piston install ? Rod bearing or retainers ?

Hoping this will turn into a new favorite saw after it's done, appears to be in pretty good shape other than the piston.

Thanks for the help.
 
pioneerguy600

pioneerguy600

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Good to hear, I've got the carb kit, piston, rings, seals, fuel line, impulse line and gasket already. Probably get going on it next week, I want to sneak up North and open up the cottage while it's in the 70's there yet this week, this looks like a good rainy day barn job :)
Those are the best days for working on saw rebuilds, have done the same untold times. A little port work and put a 3/4" exit hole on the muffler really wakes up an 026.
 

SteveSr

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Morning all, I picked up a "Somewhat running" Stihl 026 a few weeks ago. It will start but runs poorly, pulled the muffler and the piston is scored so I am going to pull the top end to replace the piston and cylinder if necessary. Hoping to save the cylinder, but I'll see what it looks like. The piston isn't too bad so I'm hoping the cylinder isn't damaged beyond repair. I figure while it's apart I may as well replace the fuel lines and crank seals as well, check the intake, rebuild the carb. Anything else worth looking at or doing while I'm there ? I'll check the condition of the AV parts and all as well.

I've worked on mower and tractor engines for years but this will be my deepest into a chainsaw. Any tips or tricks on the 026 ? (It looks to be an older model with the Wt-194 carb and the old style air filter, no de-comp) Just looking for any advice from those that have pulled these apart before so I don't do anything silly or make something worse. I looked up the posts on cleaning up cylinders, that should be no problem. Any tips on the ring and piston install ? Rod bearing or retainers ?

Hoping this will turn into a new favorite saw after it's done, appears to be in pretty good shape other than the piston.

Thanks for the help.
Best tip, as with any saw, is to clean everything up BEFORE you tear it apart to keep crud out of the crankcase. only have to block the intake, exhaust, and pulse.

Circlips get installed with the gap pointing either up or down.
 

drf255

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Take lots of pics as you go along, so you can reference later. Pics help if you have questions here as well.

Most importantly, remember that the saw is scored. You’ll need to figure out why that happened in the first place. Make sure you vac and pressure test it before the first run. Check both crank bearings and the both rod bearings for wear and tear. The crank bearings are very oversized on the 024/026 and rarely go bad. The PTO bearing is the same size as an 046’s, and the fly bearing is just a narrower 6202.
 

kevin j

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Since you got it scored and don’t know the history and haven’t heard it run, I would pressure vac test before you tear it apart. Then widen the exhaust port. don’t change the timing top or bottom. make sure it’s properly chamfered and deburred. add a couple more 5/16 holes in the muffler baffle. When you put it back together check your squish clearance. you probably can delete the gasket. Makes it a whole new saw.
 

Kevin GB

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Been up North at the cottage for a few days and finally got around to taking it apart this afternoon. Looks like the intake boot was the root cause for the piston damage, it was torn pretty bad. The exhaust side of the piston/cylinder didn't look too bad but more around the intake side. Cylinder cleaned up pretty good. Ordering a new intake today, looks like I have all the other parts I need.

Any tricks to getting the new intake through the housing hole ? Looks like a pain in the a$$. Also any tips for popping and installing the crank seals ? I have them so I figure I may as well do them while I have it apart.

How much would you widen the exhaust port on each side ? Just pencil grind it out ?

Thanks everyone for the advice so far. Worked on an outboard and a saw today, not a bad day :)
 
Mad Professor

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Been up North at the cottage for a few days and finally got around to taking it apart this afternoon. Looks like the intake boot was the root cause for the piston damage, it was torn pretty bad. The exhaust side of the piston/cylinder didn't look too bad but more around the intake side. Cylinder cleaned up pretty good. Ordering a new intake today, looks like I have all the other parts I need.

Any tricks to getting the new intake through the housing hole ? Looks like a pain in the a$$. Also any tips for popping and installing the crank seals ? I have them so I figure I may as well do them while I have it apart.

How much would you widen the exhaust port on each side ? Just pencil grind it out ?

Thanks everyone for the advice so far. Worked on an outboard and a saw today, not a bad day :)
Wrap some yarn around the intake boot a couple/three turns. Pull the boot through the housing with the yarn ends, help the boot fit with something blunt that won't tear it. I use an old toothbrush handle I've filed down at the end. That comes handy for pushing in rings too as it won't mar a piston.

Pull one of the tag ends on the yarn and it pulls right out. jug and string trick.jpg intake boot pulled through.JPG rings w:toothbrush.jpg
 

Kevin GB

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Very good, I would have tried to push it into place and probably done more harm than good. That's why I like these places, the pictures really helped.

Any tips for the crank seals ? I would usually either use a pick or a drywall screw but these are a bit smaller than I am used to.
 

Gaudaost

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Some excellent advice here. Take lots of photos, use the service manual, work methodically, clean every part really well, consider loctite, use a torque wrench on case and cylinder screws. Don’t over tighten bolts, keep bolts in place with cable ties so you know
what goes where, don’t work on it when you’re tired or not in the mood. Double and triple check things, don’t even consider starting a rebuild without a pressure and vacuum tester. Test all rubber lines, vents, gaskets, seals, tanks etc with the pressure and vac tester.
Only use OEM parts.
 

drf255

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Very good, I would have tried to push it into place and probably done more harm than good. That's why I like these places, the pictures really helped.

Any tips for the crank seals ? I would usually either use a pick or a drywall screw but these are a bit smaller than I am used to.
Tap one side in with a small punch. The other side will pop out a bit, making it easy to pull out with needle nose pliers.
 
Gaudaost

Gaudaost

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One other thing. Don’t hit the crank shaft with a steel hammer to remove a flywheel. In fact don’t hit a crankshaft with any hammer. Far better for everything, yourself included, if you buy a puller. For the 026 they are literally a few dollars... You even slightly bend a thread and it’s a PITA. You bend the crank shaft stub and you’re in another world of hurt. A 10 dollar puller is far better an investment than a second crank. I now own 8 pullers. Took damaging a crankshaft stub on an 07 to realise 8 pullers are still cheaper than a single even second hand crank..
 
Kevin GB

Kevin GB

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I agree, I have pullers but that flywheel was still pretty tight to get jaws on. I'll take a picture of the intake later, it was almost torn in half. Ordered a new intake yesterday, just waiting for it now. I'll do the seals today since they're not in the way of anything else.
 
Gaudaost

Gaudaost

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I agree, I have pullers but that flywheel was still pretty tight to get jaws on. I'll take a picture of the intake later, it was almost torn in half. Ordered a new intake yesterday, just waiting for it now. I'll do the seals today since they're not in the way of anything else.
Yes a 3 jaw puller isn’t ideal on that flywheel as the case half gets in the way. It is designed to be removed using a threaded puller which is screwed onto the centre of the flywheel. That is the held in place wjth a spanner while you rotate the centre bolt which puts pressure on the crank to pop the flywheel off.
 
Mad Professor

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I agree, I have pullers but that flywheel was still pretty tight to get jaws on. I'll take a picture of the intake later, it was almost torn in half. Ordered a new intake yesterday, just waiting for it now. I'll do the seals today since they're not in the way of anything else.
Stihl puller threads into flywheel and center bolt pushes on crank stub. Same one fits many Stihls. Don't have part # handy

flywheel:puller.jpg

Puch makes a similar one for motorcycles/bosch flywheels that has two different threads/sizes to fit/work with different flywheels. I can't recall which thread works with mid-size Stihls?

26mm x 1.5mm on one side and 22mm x 1.5mm on the other < $20 on ebay shipped

1 flywheel puller.png
 
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