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Chainsaw Top End Rebuild Tutorial

Started by Bob Smalser, April 02, 2006, 09:08:10 PM

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Bob Smalser

Have a trashed chainsaw?  Father-in-law is 84 and doesn't see so well any more...don't know what he put in the fuel tank but is sure scuffed the cylinder walls and piston to the point where the saw wouldn't run any more.

A 20-year-old Stihl 026 Farm Boss worth maybe 250 bucks....not economically repairable at the saw shop.  But I did find a NOS Stihl top end rebuild kit on Ebay for 50 bucks,  a gasket set for 8 bucks and a service manual for another 8 bucks so for that amount it was worth doing.  These rebuild kits are $135-150 retail from Stihl.

The new cylinder was the newer type with the compression release.  Couldn't find one on-line so I go see Howard at Belfair Power Equipment to see if he had an old trashed cylinder with one still in it I could recover.  He didn't, but pointed out that the new piston in my rebuild kit was no higher compression than the original, and that I could live without the release.  He didn't have the special bolt to plug the hole, so I hit the hardware store for a machine bolt and copper washer I could grind to fit...which I did.



Dismantling the saw to expose the cylinder, I discover all the machine screws are Torx headed.  I've got those for all except the long-reach Allen-style wrenches needed for the cylinder head-to-crankcase screws, but I discover a 9/64" Allen will break them loose without damage so I proceed.  You can see the wrench reaching thru clearance holes in the cylinder fins to get to the machine screw in the pic above.



The hose clamp on the rubber intake manifold is loosened and the cylinder head pulled from the saw...



The shiny new piston is fitted to the connecting rod using the old spring clips...everything lubed with 90wt oil and swab...



The rings aligned per the book and compressed with a hose clamp...a new crankcase gasket installed...



And the new cylinder...also liberally lubed...tapped on, displacing the hose clamp which is dismantled and removed.  You can see the loose hose clamp below the cylinder.



The cylinder screws are replaced and torqued, and the spark plug is grounded to check for spark with a pull of the cord before installing the plug.



The carb, which had been washed in carb cleaner and had been soaking in solvent, was reinstalled with it's linkage and a new gasket...fresh fuel added after cleaning out the tank and filter...and she fires on the 3rd pull and both runs and idles well...I got lucky for a change.



Shrouds, handles and covers reinstalled, and Pop has a working saw again....only this time...I'll supply 5 gallons of correct fuel so he doesn't run out.

$66.00 and about 2 hours...as opposed to ever $300 at Howard's saw shop.


Bob

Tom

I'll bet that was a good feeling when it poppedwhen you pulled the cord.  :D

thecfarm

I hope I'm still using a chainsaw at 84.Lucky him.I'm glad the saw came out well.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Kevin

Very nice Bob!

Good idea to lube all the parts with oil.
Good job.

TexasTimbers

Good work. Bet Pappy is happy.  8)

Only thing I might have done different is hit the saw with a high pressure cleaning prior to breakdown. Just makes it easier to keep from contaminating the new parts with grit and grime. I'm sure you were careful though. Nice work and thanks for sharing.
The oil is all in Texas, but the dipsticks are in D.C.

Minnesota_boy

Nice tutorial.  I might have skipped the hose clamp though.  The cylinders have a taper at the bottom for starting the piston.  You have to be very careful to have the rings lined up in thier grooves or you can break a ring doing it my way.
I eat a high-fiber diet.  Lots of sawdust!

boboak

  Bob...great tutorial.  Thanks...this one goes in the "save" pile.
Sometimes you get things done faster if you do them slower

Onthesauk

Believe Bob needs to remove the "I'm new" from his profile.  A number of great post and good info in such a short period of time.  Really appreciate your input!
John Deere 3038E
Sukuki LT-F500

Don't attribute irritating behavior to malevolence when mere stupidity will suffice as an explanation.

Alta

Nice pictorial of the process. I always use new clips because they are cheap and come with the p&c kit, and i use ATF for my assembly lube. 90wt seems heavy to me but I never got an official opinion on this - just my best guess at a good assembly oil. comments? Also I have the cheap plastic ring compressor that when lubed with ATF works like a charm and is very easy to remove when the piston slips in the cylinder.  On the wrist pin clips I found these to be a chore to install so I bought the tool - a very cool item but WAY over priced ( didnt come out of my pocket), and I also bought the Stihl torx 1/4 drive tool to torque the cylinder screws. In the past I always just got them good and tight but I like proper specs so now I can torque them properly. I have a long snap-on torx bit but its not long enough and I couldnt find anything else on the market. I considered making one when I found that Stihl had the proper tool - for $40. But now my life is simpler and I know how many inch pounds Im torquing the little screws to. Also Stihl comp releases are around $25 and the block off plug usually comes with the P&C kit. I have some spares if you want one but it sounds like you got that covered.

Tony_T

Nice work and pictures. 

The only things I'd do different would be Gunk the saw and hose it off before tear down and to replace the wrist pin/top end bearing/ pin clips; especially the clips.

For assembly lube the same oil you use in your mix works great, it's what lubes everything when it's running.


Burlkraft

Way to go Bob 8) 8) 8) 8) 8)

That was a great feeling wasn't it. I love it when things go well like that ;D ;D ;D
Why not just 1 pain free day?

CaseyForrest

Quote from: Alta on April 04, 2006, 02:39:02 AM
Nice pictorial of the process. I always use new clips because they are cheap and come with the p&c kit, and i use ATF for my assembly lube. 90wt seems heavy to me but I never got an official opinion on this - just my best guess at a good assembly oil. comments? Also I have the cheap plastic ring compressor that when lubed with ATF works like a charm and is very easy to remove when the piston slips in the cylinder.  On the wrist pin clips I found these to be a chore to install so I bought the tool - a very cool item but WAY over priced ( didnt come out of my pocket), and I also bought the Stihl torx 1/4 drive tool to torque the cylinder screws. In the past I always just got them good and tight but I like proper specs so now I can torque them properly. I have a long snap-on torx bit but its not long enough and I couldnt find anything else on the market. I considered making one when I found that Stihl had the proper tool - for $40. But now my life is simpler and I know how many inch pounds Im torquing the little screws to. Also Stihl comp releases are around $25 and the block off plug usually comes with the P&C kit. I have some spares if you want one but it sounds like you got that covered.

Depending on what ATF you are using, some have friction modifiers added to them. I believe its Mercron, for Ford trannies. Not a good thing to have in a new cylinder and piston. I too use straight 2 stroke oil as pre assembly lube.

Bob Smalser

Storebought assembly lube is fairly heavy and sticky stuff so it clings well.  When I'm out of it, I use 90wt and a swab.  You could use just about any other motor or 2-stroke oil.....what's important is that you lube liberally as you go, not what you use.  All ATF's are is 10wt oil glorified with a few fancy additives.

I also recommend using a well-lubed ring compressor of some sort if you haven't done this before.  Rings are easy to break and the kits generally don't provide spares.

New wrist pins and clips are always a good idea.  Whether the rebuild kit you ordered includes them or not is often one of life's great guesses and PIA's, so you probably should order them seperately like I didn't.

Be careful cleaning your machines.  The important bit is to not get dirt inside to contaminate bearings and fuel, and you don't have to wash the machine at all to achieve that.   High pressure water can do more damage than sawdust and oil.

I'm a farmer, not a mechanic, but I use a lot of old iron in the business and I write these for my office-worker children to pass on manual skills and so they won't be intimidated by simple procedures.





Bob

Backcountry

Sounds like there were photos go to with this, any chance they could be resurrected? Or maybe there is another tutorial?

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