Stihl 039 Chainsaw Rebuild
- Thread starter BigBrian
- Start date
bulletpruf
Well-known member
Ok, if there's no base gasket you should be good to go.
056AV is a nice saw, but prone to ignition issues and pretty sure replacement parts are difficult to find.
finn
Well-known member
I have a 029 (previous gen 290), and the slightly larger 310 version Stihl in my collection of aging saws.
Other than making sure the spark arrestor is clear I wouldn’t recommend messing with the exhaust. It’s going to require a retune to richen it up, and the diligence to always wear hearing protection to protect your hearing.
It’s not worth risking damaging your hearing for the minor performance gains, and don’t confuse more noise with more power like most people do.
seber
Well-known member
Anyone who has a lot of experience with two stroke motorcycles will tell you that exhaust back pressure is important to a two stroke motor. Just opening the exhaust without knowing exactly what you are doing is almost certainly going to reduce the available power while increasing fuel and noise.
Too late now. I went fairly mild on the porting so it should be tuneable while increasing power.
I didn't know about the ignition issues. What goes wrong? Coil problems I imagine.
bulletpruf
Well-known member
Anyone who runs a saw with any regularity - as long as they're not a complete clusterf*ck when it comes to wrenching - should really learn how to tune one. Not difficult to do.
If you're wearing hearing protection, a slightly louder saw won't damage your hearing.
bulletpruf
Well-known member
Head on over to opeforum or arboristsite.com and check out the folks who actually dyno test saws. Bottom line - opening up a muffler, especially a restrictive one like you find on later model saws, is going to make more power.
bulletpruf
Well-known member
Lots of thread on the topic at the saw sites, but here's one - https://www.arboristsite.com/thread...em-ignition-convert-to-bosch-ignition.351529/
finn
Well-known member
The problem with these backwoods tuners, is that they only see part of the story. For example, ask them what their muffler mod does to things like piston and ring temperature, both directly related to power cylinder life, when they increase fuel flow ten percent, or whatever their muffler mods permit.
They’l look at you like you have two heads, but metal temperature is directly related to fuel flow, as is wear.
Backyard “tuners“ have no idea.
Does that mean don’t do it? That’s an answer only you and your pocketbook can give, especially if it’s a free saw.
I spent over thirty years in engine development, much of it around unmuffled dyno engines running at or above rated load and speed. I’m fortunate that I still have my hearing. Many of my former colleagues weren’t that lucky.
Well I finally got home after 3 days of sales meetings and went to put my saw together but ran into yet another problem...
The cylinder is machined incorrectly. The 2 halves of the clamshell cannot seal. The bearing recesses are machined incorrectly. I have a 3/16" gap all around when the cylinder is put together.
I even tried putting just the old bearings in by themselves and still had the same gap.
My other issues is that either the screws they sent to bolt the 2 halves together are too small in diameter or the holes in the cylinder are drilled too large as the screws literally fall through.
Frustrating...
The cylinder is machined incorrectly. The 2 halves of the clamshell cannot seal. The bearing recesses are machined incorrectly. I have a 3/16" gap all around when the cylinder is put together.
I even tried putting just the old bearings in by themselves and still had the same gap.
My other issues is that either the screws they sent to bolt the 2 halves together are too small in diameter or the holes in the cylinder are drilled too large as the screws literally fall through.
Frustrating...
My brother works at the sthil plant and we do the muffler mod to our saws without problems. If you have the commercial grade saws they can handle the little bit extra you give them without issues. I have lifetime warranties on all my sthil stuff so I don't care anyway.
That *****, I bet they sent out the wrong kit. Did you buy from Wolf Creek? I've had good luck dealing with them in the past. Hopefully they can sort it out
finn
Well-known member
Good for you, but working at the Stihl plant, and understanding the engineering that goes into an engine, including the thermal and mechanical loads are two entirely different animals.
One of our former Diesel Development engineers left many years ago to start a pulling engine business. He modifies engines that started out at 200 hp (originally) and now put out several thousand horsepower. They don’t run 5000 to 10000 hours like that, though.
Good luck.
Yep I bought it from Wolf Creek. It appears to be in the correct packaging and everything else looks like it's in the same place as the original but yeah unfortunately it's a no-go.
I've called them and left a message this morning, I'm sure they will make it right.
The carbs all have two mixture adjustment knobs so in most cases opening up the exhaust and adjusting it will give a bit more power. Engines were always limited a bit by the exhaust. Mainly cause they get loud but also to stop sparks. More recent ones also for emission regulations. If you don't care for those things there is no doubt you can get a little bit more out of it. My saws are stock, they're already loud enough...
Such minor mods will not really impact the lofe of the saw. Opening up the air filter would be worse...
Yeah he's an engineer there for 30 years. He can work every one of those motors in his sleep. It's a simple 2 strke and they are over engineered.
finn
Well-known member
Same as my friend. He doesn’t have to deal with warranty numbers, though.
He also fielded a Trans Am Camaro for many years, and, last I heard, was working on a Diesel dragster.
Meanwhile, I had to endure monthly warranty reviews looking at engines destroyed by backyard tuners that were convinced our engines were overengineered, until they weren’t.
I was joking about the warranty. My brother fixes all my zero maintenance equipment I got over 15 years on my weedeater before I cleaned the airfilter! Run ethanol gas in all of it, I can't kill the stuff.
Bad idea. The last thing you want to do is start a fire. A spark screen can be cleaned in <5 minutes with a propane torch.
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Dont run with scissors either. Been doing it on them for 40 years, suit yourself. If your unit is putting sparks out the exhaust you won't be making fires for long. We don't really have to worry about catching stuff on fire in Virginia.
finn
Well-known member
Bad idea. Wildfires just lead to more land closures.
If your screen is carboning up, it’s a sign you’re running the wrong fuel/ oil mixture, or don’t know how to tune, or perhaps both.
finn
Well-known member
Forty years ago, it wasn’t unusual for saws to run 32:1 mixtures. Modern saws, with modern low ash oils are 50:1.. I had a few of those 32:1 saws. The screen plugged. It was garbage
Sometimes old people don’t pay attention to changes in technology.
Eventually they die, though, and the technology keeps changing
I'm only 55. Been around two stoke motorcycles and sthil products my whole life. We know what works and what doesn't. Those sthil engines can take alot of abuse. We don't generally have to worry about fires on the east coast and we aren't logging. I just do stuff on my properties. My brother has a tree cutting business on the side with probably a dozen saws. I promise you it's highly unlikely that anyone on this site has more experience than him when it comes those saws. Stihl has sent him all over the world helping other plants and buying equipment to make the saws.
jblnut
ALLIANCE MEMBER
I bet you’re a good bit of fun in person seeing as how you’re such a ray of sunshine online !!
@BigBrian good to hear you got it together and running !! There are lots of saw tuning videos on YouTube you can watch but some of the best done and most informative I’ve seen have come from Gordy at WestcoastSaw.
I done a lot of rebuilds on stihl saws of this design and majority of those aftermarket kits have issues with supplied bolts wrong shoulder length for machining or casing actually will not fully fit/seat unless use aftermarket kit with the same aftermarket crank as bearing size and crank bearing width can differ just enough make it look possible until fully test the fitment .
Some of the kits reuse the stihl self tapping bolts .
I use genuine parts as much as possible as fortunate enough my Stihl dealer gives me some discount and have got oem cylinder kits from 80 to 120 bucks so savings over better made aftermarket kits is none.
Have used 32 buck fairly well reviewed chinese kit for a budget limited rebuild on a friends ms180 which did fit and work and still working but the quality was visually not amazing and for very light occasional budget build use may be best option but you gambling on what current casting is as the aftermarket brands always changing so what was good yesterday might be shite today and it certainly can be more ballache getting it all fit proper nice ...
I've used original scored cylinder with some hand polishing improve a bit and banged in a new piston over using budget chinese kits as quality fitment is perfect and from real world experience had many years use out of 2 stroke engines revived this way .
basically some scoring in a oem cylinder likely perform/last longer than the 30 buck cylinder kit shite off usual online selling platforms .
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Brilliant result
They useful size saw and perform nicely when in good service state .
I don't do much to mufflers besides drill holes a size larger and pry the ports on muffler screen cover a little larger .
I like running 45:1 mix as that what Stihl states in a lot of manuals for more heavy duty/ prolonged service use, I don't use mesh screens on my saws that do lot of running hours and firewood logging .