Chainsaw complete tear down/reassembly

Billy NY

Well-known Member
So way back when, needed a saw, farm use/firewood too but not then, researched a little, ended up with a Stihl MS 390, this was '02. I'd say after 12 years of use, it's paid for itself, done what I've needed, I'm not a logger, I don't cut daily, so this models description/1127 series Stihl family of saws seems to live up to its name.

Over time, it did not look like it did when new, usually well kept, but hauling in a loader bucket, it took a short fall when relieving an ice covered tree limb over the un-energized power line close to the weatherhead, after an ice storm, I had been meaning to make it right since.

So I started with a new engine housing, handle, flwyheel cover, sprocket cover, fuel line etc. it's been said these are difficult to work on, I did not find that to be true, there are a few things to know, the bar stud has loctite, you have to be creative to get it out, 2 bar nuts or flat spots cut with dremel, on this one I did not have to cut the flat spots for a 10mm wrench. Clutch is left hand thread. With a new engine housing, you have to tap the new holes for the screws, use care on that and it will work fine, common sense, 1/4" drive ratchet or screw driver handle with T-27 driver. Set the flywheel to coil gap with a twice folded 8"x11" sheet of paper, ( as if you were to put it in a standard envelope. New air filter, I've cleaned the old one for 12 years !!!

Boy do chainsaws get filthy, everything is covered with sawdust fines soaked with bar oil, compressed air with a fine stream tip is your friend, so is a nearby garage door to blow off the oil soaked/caked parts. Now I know why I like bar oil, it does not fling as much as other alternatives, besides what it does for the moving parts.

I was able to carefully check the carb boot to the intake, good, same with the impulse and the bar oil line, all looked fine, stretched to look for cracks, holes, carefully cleaned and examined, all pliable, and fine, I was going to just replace all of them, but they felt just like the new fuel line, if any do fail, its not that difficult to change any of them.

I am aware that this engine has plastic bearing races, which can be detected as defected by shaking the engine while out, you can hear the ball bearings moving freely, mine was good on that, the piston and cylinder look fine, still have the machining marks on the piston, I could detect no wear and by feel/listening, seemed like good compression, sure you need to test to be sure. I attribute the lack of wear to using stihl 2 cycle oil, precisely the correct amount of gasoline and oil every time, I even rinse the little jug of it with gas to get the remaining oil out, cleans it for the recycle bin, so a win-win on that LOL !

From what I saw while doing this, the materials the saw is built from are decent, all the parts are marked, there are no real pitfalls, well that's a dumb design etc. I like the brand and of course it could be another, its fun and almost a hobby but there's a few things I own that I will use exclusively, all their products. So on this saw I use nothing but Stihl products. My John Deere lawn tractor the same, these 2 and my Troy Bilt Horse, rototiller get meticulous care, seems to work, and being small its a little bit of fun. Stihl is an expensive brand name for sure, parts exclusive to dealers and probably a lot of stigma, like other brands with the same status. I would never criticize another brand until I used it extensively and took it apart and re-assembled it, knowing whats different, what I like and don't like. I enjoyed this build for some reason and thought I'd share the experience, more important than brand or what have you, it was a fun little project.

Finally time to cut again, may not look as clean again, but I will be a lot more attentive to it's care, use and most importantly its maintenance which I did all along, just did not look it LOL !

PS, I even transferred stickers/decals to make it correct, new engine housing has a blank spot where the serial number goes, so I recorded that took photos, will have to mark it somewhere hidden.
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Hello Billy NY,

That saw will be better then new! Mass assembly can't beat all the TLC you used to put the old girl back to shape. You will definatly have a good working saw for many years to come.
Excellent job!


Guido.
 
I took a few photos at various stages from the engine housing up. The one benefit of this, now I know how to take it completely apart in case of repairs. I also see its just good practice to open these up/clean repair, mostly clean. Also learned that the flywheel may rub the coil if those bearing race's fail, so I'll be cognizant of that. I figured it was not broke, so don't fix it when the motor was out. Its been said these can have leaks at the base, well it looked like the seal was good, and the only issue I did have prior was it was cutting out after a load or while a load was on it, high rev, as it slowed down, wanted to quit and stall. Fuel filter cleaned, was fine, new line, old one was only a few years old, we shall see, also re-did the spark plug end connector, stab in type, seemed a little loose, so I just poked it in a little further down, cut that much off the end, less than an 1/8", small piece of electrical tape over the old hole, then the boot. Hopefully no issues, it fired in about 4 pulls and ran flawlessly, oiled that chain so much I may back it off max, must be when they get loaded up, it was not oiling like this before, granted it left a streak if you checked it, what came out now drips off. Every part on this saw was cleaned thoroughly, oil sure makes a mess !

Thought I'd share the experience, it was fun, most parts I got off ebay, OEM Stihl, engine housing I ordered from the dealer.
 
Nice job. If you put on the wall at the dealer you would be hard pressed to tell it from a new one. I have a MS 170 that I bought in 04 when the Hurricanes came thru my part of Florida ( 4 in 6 weeks ) It has been the best small saw I have ever owned and is still running good today. In fact I bought another one just like it last year when the dealer had them on sale.
 
Hello Again,

Just curious, what did you set the plug gap at?
I find that if set @020 is a bit close. It makes the plug collect oil. My work saw with electronic coil/ignition, has the gap set @0.40. Try it! even @.030 is better then 0.20. The plug will last a lot longer, and performance is just fine.........


Guido.
 
I forget actually, Bosch from, the dealer, I thought it was preset, though I usually check before installing, have a gauge in my chainsaw tool box tray just for the saw. One thing I have never had an issue with is spark plugs in this saw, though I have changed them periodically over the years, never seemed to make a difference, I think I have all the old ones as spares too. I'll double check the next time its out.
 
Looks brand new. I don't think anyone could tell it's an older saw.
I was wanting to do the same for a 064 that I bought new in '85, but the cost of parts is very high. Did you use Stihl parts or aftermarket?
 
Sounds to me that saw wasn't used much if the piston and cylinder had no wear on it..
I had a Stihl 034 for 15 years, nothing but trouble,always hard to start cold or warm.
Wore out two pistons and cylinders, 2 oil pumps, intake boots lasted a year, 2 carbs etc etc.
And it still was POS
I was glad when i accidentally ran over it,...gave me a reason to buy a real saw.
A husky :wink:
 

This spring I found my Sthil .034AV along a fence row I was cleaning out a few years ago. I had forgotten about the saw but, there it was in the brush.

Chain and bar were shot, cylinder had scores, rings froze, carb totally plugged, points rusted shut, etc...

$155.00 later....new cylinder, piston, rings, wrist pin, carb. points, condenser and plugs....she runs like a new one.

BTW, increased the cylinder and piston size to make it a 034AV Magnum.


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I kept an eye over time on ebay for oem stihl parts, there seems to be plenty for 1127 series. Engine housing was ordered from dealer as I wanted to make sure it was new and the parts it came with. I thought it'd be fun to do this. Engine was in good shape, so was the original carb boot, impulse hose and oil hose. It seems the materials are of quality, designed for heat, a few years back, the fuel line was cracked in numerous places, it would still run, but you knew something was up replaced that an it was still good, so I kept it for a spare.

It looks like it should, even the stickers LOL factory correct LOL !!! minus the oem handle warning label in espan~ol,

It runs flawlessly, everything works like it should, made 2 test cuts on a big maple log to check the oil on the chain and see if everything is ok. Cutting speed/efficiency was good, though this is not the hard dense maple I believe. Might turn the oil up more, used to run it at max, but turned it back as it was running off a little when I set it down.
 
Think it was from wear, lot of use or just a lemon from the start ? Performance is key, brand or not, its a necessary tool for me at this time. My dad had an 08S which I still have and so I kinda went for this one, I remembered the 08S as a decent saw, so the name sells ya, LOL, though the way they build them is a lot different now.

This one was no angel, hard starter at times, but seems I've figured out you just need to keep the air filter clean, also clean, check the plug and whatever else similar. It recently was cutting out on me, before I did this work, and seems I cured that problem somewhere in the mix, it ran perfectly. The fuel mixture I use works, did not see any problems there, the oil pump checked out to be fine, piston and cylinder did look great, a little patina from glaze, piston top a little carbon residue, made the rope black I used to hold the crank still by jamming the piston. It has cut quite a few trees, some 36" at the trunk and about 5 cord per season since '08. I broke in a brand new Husqvarna 455 rancher, friend who hunts here left it here, had bar oil leak, I put husqvarna oil in it, stopped leaking, then I blocked up a couple a decent size logs, put a few tanks of fuel through it, he did hit barbed wire with it in an old tree, I sharpened that chain with a husquvarna file on my stihl bar guide, don't know much about the brand but it cut really well with a 20' bar, he used that chain awhile after too, throwing shavings in some wood, lighter too !
 
If I rebuilt or replaced the motor, in total, I think I'd still be in it for significantly less than new and in that case it would be new given what I did.

Its a good result for you too, hard to imagine forgetting one in the fence row, weathered but very functional now and that's what counts to me LOL !

Mine showed some use before, I kinda went for the dupont overhaul in a sense LOL !
 
Billy NY-_ you rebuilt a good saw and did a fantastic job in doing so. It looks great.

The way I see it is you have a "new" saw for far less $$ if had bought it 'new'.

I will bet it will last you a very long time.

Greg
 
We had an 038 bought new many years ago and it felled (and cut into firewood ) many a tree , including some big old dead elms and oaks. We ran it for about 15 years All it ever needed in all that time was new chains and guide bars. Then when we sold the farm in 1996 I kept it and stored it in my garage. These days I hardly need the use of a 'big' saw, so for tree pruning and general maintenance I use a little 017 ( I have cut a lot of firewood for others with it too) and I use a FR130 Backpack Brushcutter almost daily which has never given me a pennyworth of trouble.
I dug out my trusty old 038 the other day, It has not been used at all for at least 18 years, I put some fuel and oil in it, primed the carb' and it started 3rd pull! You can't beat Stihl!
 
Hello Billy NY,

A Spark plug is not set. It fits more then one engine, and not always gapped the same between engine brands. What actually happens the gap gets beat in during shipment. I've seen the gap on them be close to zero when new. I'm always amazed how the engine starts with such a small gap! Check it.........Bet you the gap is 020 or less!

Guido.
 
I just finished reworking an old Stihl 028 Super AV. It had not been started for probably over 20 years, and was my fathers saw that he purchased new. He told me that it locked up, and just bought a new 029. After his passing in 1999, for some reason I kept it around and had robbed a few parts off it including the chain, and fuel cap. One day I was getting ready to toss it when I gave it a pull on the rope, and discovered it was not locked up at all. After giving up on getting it started I found that the cylinder was indeed heavily scored, likely due to mistakenly running pure gas in it, but I guess I will never really know. I ended up rebuilding the carb, replacing the fuel line, filter, and pulse hose, and bought a used cylinder off ebay, and it seems to run pretty nicely now, and plan on using both his old 029 as well as this one. Part of the reason I decided to fix the 028 was that I noticed the prices on used saws similar. I ended up with less than $100 invested in the 028, but still need to check the oiling on it was it seems like the bar/chain is not getting enough oil.
 
I remember my fathers 08S hanging on the wall for years, never saw a lot of use either, though we did cut wood for the fireplace, and the stove here later on, it sat mostly. Was '97, I did not own a saw, but I needed to do some trimming and some clearing, it has the tillotson carb, so I took it apart, and just cleaned it, no kit, it fired and ran great, now need to do the same, got another 08S that runs, at a garage sale, $30, and an 015L or R I forget now LOL, it runs, both those need to be gone through, next on the work bench, see how it goes. I'm not a fanatic, but I do like the brand so far LOL !
 
I think it can be a worthwhile endeavor, I may play around with more of these, I see someone constantly listing used stihl saws on CL, seems to fix them up and repair etc. Most retain the "cosmetic wear", it was enjoyable work to fix mine up to look like new though. It seems cost effective, put a good or rebuilt engine in one, build the rest with new parts or what have you, seems you can't go wrong. Besides fuel lines and or parts that are rubber, I think a lot of it is on the end user of these. I was very conscious of the fuel mixture I used, actually ran high octane, stihl oil, and for the past several years I've treated the fuel with startron. I saw that the piston appeared to be well lubed, and hardly any wear, it starts easily and ran flawlessly yesterday, seems what I did was well worth it now.

My neighbor owned a power/small engine equipment and saw shop for the better part of 50 years, his dad started it. Neighbor retired, sold his interest in it to his partner, not sure how that went, but he works there part time and is one of the nicest people I have ever known. They sell Husqvarna and Echo, both good brands. I should ask him about the things that cause the most problems by the end user, they always have 2 or 3 shelving racks full of customers saws in for work, any time you go there. They always treat the customer right there, always have.
 
I can tell you what I see Billy, the end used issues I mean.

1- Never, ever cleaning the saw, not even a little.

2- Never, ever cleaning the air filter, much replacing it when it's torn or rotted.

3- Never ever doing any up keep in the B+C, like dressing the rails or even seeing if the oiler works.

4- Grease the roller nose? Ya mean I gotta GREASE IT?

5- Stale fuel.

6- Ethanol. I don't care what anyone says, it is a problem.

7- Mix oils that were great back in '66 (ie- 30 wt, 10-40, etc) and mix ratios of the same period (16-1, 20-1, 25-1). Put that stuff in a late model saw and you are asking for problems.

8- Dull chains, bad sprokets and rim drives.

9- LEANING ON THE SAW. Just because it's got those log spikes on the front doesn't mean you need to horse the saw into that 32" hunka white oak or rock maple. These are the guys that need new AV mounts 3x a year.

10- Heat. Ya don't ever clean it, ya don't run a good oil or mix, ya lean it out till it screams and then you wonder why it runs so hot that it melts the cover and later the piston.
It's your fault, not the saws, not the fuels, not the oils.

I'll stop there.
 
I would absolutely agree! I won't claim to have much knowledge of a chainsaw in my younger days. So I'd say 12 years ago, besides the 08S my father had, which I did use occasionally, most of this was new to me. Maybe its me, but I've learned a lot about bars and chains and saws in general for sure, and certainly that nose sprocket, after dropping a bar tip first into loose dry dirt ! LOL boy was that a time consuming task to get all the grit out.

Maybe people ignore these things, but when that bar needs to be surfaced or the side edges are curled over, you need to deal with it. Both bar and chain with problems, they cut poorly for sure.

Any special lube for these bar tips ? White lithium ?

Air filter, its wise to carry spares, those darned things just load up, even with the intelli-carb, you have to split it and clean with compressed air in regular intervals, mine would be a hard starter and I think it caused stalling.

Unfortunately, I can't find non ethanol gas nearby, so I treat it, but one fuel line did crack in numerous places on this one, dried out somehow. I use 93 octane, stihl oil, and startron.

Dull chains are a waste of time, make dust not chips and the saw revs high, with little work done. Worn sprocket, can't maintain tension, could toss a chain, at 50 mph, I don't need that.

Knowing air cooled engines deal with a lot of heat, I try not to use max rpms throttle, I take my time, by the same token I don't lug or use it so the combustion chamber loads up. I've also made sure to let it idle down if I need to shut if off after a long cut, let that air flow to cool it off, not long enough to load up but..

Cleaning, the air fins on the motor, some are obscure, I saw the value of taking this one apart and cleaning those, I would highly recommend the practice. The other thing that came to mind was more viscous bar oils, like at the auto parts store etc, those fling off more and make so much more of a mess, I have to believe they cause more build up in places you want clean, I did try other oils and noticed how sloppy they were. The stihl brand and Husqvarna brand of bar oils, seemed alike and did not do this, for the cost and how much I use, it saves me nothing to not use it.

Those 10 items, over time, to me, became obvious from experience, many people don't pick up on these things, so maybe this thread will help someone, thanks for posting that, likely the same thing the saw shop guy would have said, and I assume you have seen the same from working on them over the years.

Some of these things are safety concerns, personally, I take it seriously. I have noticed the difference in the new 20" bar and the old one, I should have tossed the old one, saw shop guy said he could re-surface it, was ok on the less used side, but I noticed a wave to it, likely from the occasional pinch over the years, so its done.

This saw does not like you to lean on or apply significant force to it, you can easily pop one of those rubber dampeners, at some point mine did, the cap on it melted away, new one came with the engine housing. Seems with the stock log spike or the more aggressive pair you you easily put on, with a sharp chain, it should just pull itself in, till you have to stop, roll the log etc. Pushing on it will accelerate wear to the bar surface or so it would seem ?

I've cut some wood with this one, it runs like a new one, I'm happy with the results so far ! It just seems right to show some respect for these kinds of outdoor power tools.
 

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