Part Two: The Intake Port

[Stump Shot]

Ya'll about the nub tonight....

The nub, not the Dub.

 

[Dub11]

Do we win anything?

Nubs?

The nub, not the Dub.

Leave me out of this.
I ain't that narcissistic

 

[drf256]

That’s a strato intake. That’s gonna flow fuel rich charge.

Just be careful moving things. Gotta remember that greater than what you expect of your intake area is through the stratos.

Dropping jug is gonna open stratos and fill the uppers sooner already. The time open shouldn’t change.

Plus you’ve got a complicated piston there with a tiny intake skirt.

 

[drf256]

Intake port shape is likely designed that way to keep the rings tucked in when the piston is at BDC. Check out the ring pin locations and compare to intake port. Last thing you wanna have happen is have the saw hang a ring in a port.

Really does look like it’s on opposite side for most Stihls.

 

[XP_Slinger]

Measure the skirt between the cut outs on the piston, then measure the width of your intake. You might not have enough room to widen the intake without exposing the cut outs...which would be bad, intake would never close.

 

[Mastermind]

Just lower the floor of the intake 1mm. Leave the rest alone.

 

[Deets066]

I'm just a hobbyist porting my MS 241. I've checked out @Mastermind's build and reviewed @Keith Gandy and him go back and forth on the build.

• It seems that @Deets066 and @mdavlee advocate for a rounded rectangle. Stock is squarish with some kind of weird nub in the corner. I can't figure out what nub is for. I channeled my inner ape, and I can't figure anything on the piston or lower that makes the nub necessary.
  View attachment 158351 View attachment 158352
  
• Right now I think I have 145* of opening. The port is currently .560 wide, and the piston skirt is .742, leaving me .182 to split. How much support does the intake need on each side?

I like to shape em like this, could’ve squared the bottom right corner a little more....

 

[Mastermind]

View attachment 158379

I like to shape em like this, could’ve squared the bottom right corner a little more....

My right or yours?

 

[Fairways_and_Greens]

Not if it's doing it's job.
Mark the piston at bdc and remove the cylinder to see where the ring is

So I don’t have a felt pen that can fit into that little port. What do you guys use to mark?

 

[Fairways_and_Greens]

That’s a strato intake. That’s gonna flow fuel rich charge.

Just be careful moving things. Gotta remember that greater than what you expect of your intake area is through the stratos.

Dropping jug is gonna open stratos and fill the uppers sooner already. The time open shouldn’t change.

Plus you’ve got a complicated piston there with a tiny intake skirt.

Thanks. I’ve read through the transfer port thread in advance of this this to get the big picture. Not a ton regarding stratos in there. Do I need to raise the strato on the jug to recoup timing or am I asking for trouble?

 

[Fairways_and_Greens]

Just lower the floor of the intake 1mm. Leave the rest alone.

Thanks Randy. Intuitively I would have taken off the roof because the jug is lower, thanks for saving me. Since I don’t have the benefit of your experience, how would I have figured that one out intuitively? (Beyond the wise ape adage “test, test, test”)

 

[huskihl]

So I don’t have a felt pen that can fit into that little port. What do you guys use to mark?

Sharp pencil

 

[Deets066]

My right or yours?

Yes

 

[Fairways_and_Greens]

View attachment 158379

I like to shape em like this, could’ve squared the bottom right corner a little more....

So your ports can look like that because your lower ring is above the intake at BDC?

 

[Deets066]

So your ports can look like that because your lower ring is above the intake at BDC?

Yes

 

[Deets066]

So your ports can look like that because your lower ring is above the intake at BDC?

Every saw is different, there are lots of things to consider before you start grinding away

 

[Mastermind]

Thanks Randy. Intuitively I would have taken off the roof because the jug is lower, thanks for saving me. Since I don’t have the benefit of your experience, how would I have figured that one out intuitively? (Beyond the wise ape adage “test, test, test”)

How much lower?

 

[huskihl]

So your ports can look like that because your lower ring is above the intake at BDC?

Normally, but not on a 241

 

[Deets066]

Thanks Randy. Intuitively I would have taken off the roof because the jug is lower, thanks for saving me. Since I don’t have the benefit of your experience, how would I have figured that one out intuitively? (Beyond the wise ape adage “test, test, test”)

If you lowered the jug you’ve already lowered the intake

 

[Fairways_and_Greens]

How much lower?

Gasket thickness.