044 conversions-10mm to 12mm,12mm to 046?

[skip sail]

I have several 044's in various stages of "expansion" (you know,when a saw frees itself from the constraints of its condensed form and spreads itself around the workshop to mingle with its brethren)

A couple of 10mm wrist pin models and a couple of 12's.
There isnt a serviceable jug for the 10mm,but i have a couple of nice 12mm cylinders.
According to what I've been told,its fine to put a 12mm cylinder on a 10mm saw,without any problems.
anyone with experience in this, ie pros and cons,pitfalls etc?

So then i'm wondering about using the 12mm saw to build a hybrid, using an 046 cylinder and piston
once again,any thoughts on this process?
thanks fellas
Skip

 

[Chainsaw Jim]

I don't believe there are such things as 10mm or 12mm specific jugs.

 

[skip sail]

they differ in the cooling fins

 

[fearofpavement]

Just make sure you have the right piston as those are not interchangeable.

 

[Gunn]

10mm piston will risk hanging a ring if run in a 12mm jug, but 12mm piston in a 10mm cylinder is ok.

 

[Nitehawk55]

Stihl went to 12mm because the 10mm was a weakness in design .

 

[fearofpavement]

Stihl went to 12mm because the 10mm was a weakness in design .

A lot of people would disagree with that statement. I have both and don't really notice much of a difference between them.

 

[Chainsaw Jim]

10mm piston will risk hanging a ring if run in a 12mm jug, but 12mm piston in a 10mm cylinder is ok.

Those who widen the intake even the slightest are at a higher risk. The intake on the 440 cylinder is about 1mm wider, so I don't believe that creates a real concern.
Both pistons look to share the same locating pin location as far as I can tell and I'm looking at three 10mm oem and two 12mm oem here in front of me.
It's hard to tell without the correct measuring equipment.
The port shapes and locations can vary from cylinder to cylinder on the same model of saw that never made piston changes like the 460. So it's kind of hard to set a standard on the 044/044/440 cylinder differences if 1mm is a difference between the early ks slant fin and the 440 with decomp. I have a straight fin that matches the early slant but not sure which saw that came from.
So now I'm good and confused about it.

 

[Deets066]

they differ in the cooling fins

Early 12mm jugs had slanted fins also, I used to have one but sold it to Dave

 

[Chainsaw Jim]

I'm up for learning all I can about this subject.
One question I have is how do you know which cylinder is the earliest one? One plus mark? Or no plus mark?

 

[Deets066]

@Definitive Dave is a 044/440 connesieur

 

[dall]

id like to know the differences also i have a couple slant fin ones

 

[skip sail]

I'm looking to buy a clean 10mm slant fin jug if anyone has one?

 

[drf256]

Interesting stuff boys.

I've never measured the skirt width on meteor vs. OEM 044 slugs. The 10mm Meteor casting had a flaw in design, the pin bosses were the same width as the 12mm, so there was a ton of play back and forth. I'm not sure if that's changed or not, and I haven't heard of any real issues with them. I'm wondering if the 10mm meteor has a wider pin location and allows the use of a 12mm jug on a 10mm case. It seems to be a knockoff of the 12mm with a smaller ring bore.

I can tell you that on an 046, the meteor casting has a much wider skirt than OEM. I wish I had measured them side by side, but I recall it being 4mm+ wider than OEM. When I ported @MustangMike 046 jug, we noticed that.

 

[MustangMike]

I'm up for learning all I can about this subject.
One question I have is how do you know which cylinder is the earliest one? One plus mark? Or no plus mark?

My understanding is that they added plus signs to note revisions, so the more plus signs, the newer the jug. Earlier do not always run better. My best stock jug is a KS jug in the 126****** SN range, it is a red lever saw.

 

[MustangMike]

I'm up for learning all I can about this subject.
One question I have is how do you know which cylinder is the earliest one? One plus mark? Or no plus mark?

My understanding is that they added plus signs to note revisions, so the more plus signs, the newer the jug. Earlier do not always run better. My best stock jug is a KS jug in the 126****** SN range, it is a red lever saw.

 

[jacob j.]

There was a service bulletin issued by Stihl saying not to use OEM 10mm wrist pin pistons in later cylinders, because the ring locating pins are much narrower on OEM 10mm wrist pin pistons and you will hang a ring if used in a later cylinder. I have the service bulletin at home and will post it later tonight. That being said, most of the aftermarket 10mm wrist pin pistons I've seen have wider ring locating pins and are fine to use in any of the cylinders.

Nighthawk is correct- the reasoning behind redesigning the saw with the 12mm wrist pin crank was due to the high number of big end rod bearing failures on 10mm wrist pin cranks. A service bulletin was issued by Stihl for this also. It was brought up at a dealer update meeting years ago.

 

[Definitive Dave]

the "+" signs denote later casting runs in the same mold series so just looking for fewer "+" signs doesn't get you an early cylinder
the different makers used different letter and number combinations to designate mold series in case of the need for later recall, but as far as I know there is no definitive listing for cylinder mold series to serial number range
If you want a great 044/MS440 without an actual port job, use an OEM piston appropriate for your crankcase (meteor is ok for the 12mm or even for the 100mm in my book, but opinions vary) and get a nice clean slant fin jug.
If you are having it ported go modern and ask your builder if they have any preferences.
Dave

 

[junkman]

10mm piston will risk hanging a ring if run in a 12mm jug, but 12mm piston in a 10mm cylinder is ok.

+
This is what i have been told for a rule of thumb ,but i have seen a few 10 mm saws with later jugs on them and not hanging rings ,a guy can move the pins on the piston if needed also .

the "+" signs denote later casting runs in the same mold series so just looking for fewer "+" signs doesn't get you an early cylinder
the different makers used different letter and number combinations to designate mold series in case of the need for later recall, but as far as I know there is no definitive listing for cylinder mold series to serial number range
If you want a great 044/MS440 without an actual port job, use an OEM piston appropriate for your crankcase (meteor is ok for the 12mm or even for the 100mm in my book, but opinions vary) and get a nice clean slant fin jug.
If you are having it ported go modern and ask your builder if they have any preferences.
Dave

I always thought a jug with more + signs was more defeats over husky's when racing .

 

[Definitive Dave]

+This is what i have been told for a rule of thumb ,but i have seen a few 10 mm saws with later jugs on them and not hanging rings ,a guy can move the pins on the piston if needed also .
I always thought a jug with more + signs was more defeats over husky's when racing .View attachment 26530

also leave out the bottom ring cause if you are going to this trouble you want a fast one anyway
if they added a "+" for every husky defeated the outside of the jug would look plaid!!!