Stihl 024 New project

[Tpagel]

Thanks for the quick responses
It is a 026 case crank and jug now but still small
I am a firewood weekend cutter and don't want to lose a usable saw because I have a boner to make it faster


Sent from my iPhone using Tapatalk

 

[pioneerguy600]

The 50 cc saws on average need more compression degrees to give them more grunt for firewooding/woods work. I have built several dozen 026 - 260 saws now and try to get minimum squish, highest comp and the highest number of compression degrees I can work into these saws, a little work on the intake and a ignition advance along with the muffler match plus open up the muffler exit hole.

 

[Tpagel]

I ended up leaving the transfers alone and only widening the intake and exhaust well within my do not touch lines.
Then I polished the exhaust as smooth as I could get them with paste and a cotton buff. I see why people pay big bucks to have a pro do this.

Sent from my iPhone using Tapatalk

 

[drf255]

I ended up leaving the transfers alone and only widening the intake and exhaust well within my do not touch lines.
Then I polished the exhaust as smooth as I could get them with paste and a cotton buff. I see why people pay big bucks to have a pro do this.

Sent from my iPhone using Tapatalk

Your "DNF" lines are off.

 

[Tpagel]

??? How do you tell

I wiped most of my ink off so I can't go back and check the lines left were where I traced down the locater pins on the piston


Sent from my iPhone using Tapatalk

 

[pioneerguy600]

You are dangerously close to going beyond the width of the piston skirt, you need to map out both skirt lines for intake and exhaust, the piston skirt acts as the valve so the width of a port must not go wider than the skirt will cover.

 

[SEAM]

Too wide will cause the ring to expand into the port an get caught...

 

[Tpagel]

Ok I will bolt it back on and mark again and see if I made scrap metal.
Thanks to everyone


Sent from my iPhone using Tapatalk

 

[Tpagel]

Right side exhaust is too wide as you all said
with flashlight I can see a crack on between the skirt edge and my crappily ground port
More reading before I start over.


Sent from my iPhone using Tapatalk

 

[drf255]

It may still run. Are you sure you see a space between the piston skirt and the exhaust port? It's easy to be deceived by the viewing angle.

The intake port (as you view it in your pic) is too wide on the LEFT side. Common rookie mistake area, as the port direction guides you towards doing that. IIRC, that's the lower ring pin's location. You can run it with a single top ring. It will actually make more rpm that way.

Don't forget, if you're able to salvage the cylinder, you need to chamfer all the areas you ground.

And yes, until you do a jug yourself, you don't understand why porting costs so much. It's actually a bargain at $300. If you don't enjoy the game of porting itself and are just looking for gains, it's not worth doing it yourself.

 

[Tpagel]

Again thanks for the advice I like the idea of making the gains myself on saws. I guess I just got carried away with the grinder.


Sent from my iPhone using Tapatalk

 

[pioneerguy600]

The layout takes the most time and patience but is very necessary to prevent mistakes, the grinding is the most fun and provides the satisfaction factor. Porting does take time and you will learn as you go but mistakes are almost certain unless a lot of time is spent on the layout lines.

 

[pioneerguy600]

I will just throw these picts up on here, maybe they will help a little, notice the double lines on the intake side, one set denotes the max width of the port and the second set denotes the ring end pin location,

The exhaust side only requires a single set of lines to denote the max width of the port,

the exterior of the exhaust port on a common Stihl jug,

all of this work was rough in before final polish.

 

[Tpagel]

I will just throw these picts up on here, maybe they will help a little, notice the double lines on the intake side, one set denotes the max width of the port and the second set denotes the ring end pin location,

The exhaust side only requires a single set of lines to denote the max width of the port,

the exterior of the exhaust port on a common Stihl jug,

all of this work was rough in before final polish.

That is awesome and a great help I will use these
I have another jug to map out in the shop at work.
Plus a 024 p/c where this all started.
I think it is a good idea for me to map everything I have before I grind anything.
After looking at this mine lines were very inadequate.


Sent from my iPhone using Tapatalk

 

[pioneerguy600]

A very sharp lead pencil makes fine lines for porting, I find any type of ink felt tip marker will bleed out and make the lines too thick to be accurate.

 

[merc_man]

A very sharp lead pencil makes fine lines for porting, I find any type of ink felt tip marker will bleed out and make the lines too thick to be accurate.

Howbdo you determine how wide to go on the exhaust port?

And do you widen the intake at all?

From what i read that if you widen the exhaust will give you more torque not rpms.

Sent from my SGH-I747M using Tapatalk

 

[pioneerguy600]

Well now on the Stihl saws only the port width is determined by the piston skirt width, enough cylinder wall needs to be left for the piston skirt to effectively seal the port opening. Other saws may be the same but others will have wider skirts so then the 80% rule has to be followed, that`s 80% of the cylinders width measured on the cylinder surface. I widen both intake and exhaust ports. What affects RPM the most is raising the exhaust port roof increases RPM but loses torque, gaining a bit by lowering the jug will give a bit of extra torque without affecting the RPM much. Running one ring will increase RPM somewhat due to less drag, jury is out on if one ring will last as long as two and make the same compression.

 

[Stihlofadeal64]

Only wish I could walk through this looking over a person's shoulder -- step by step. Perhaps some day.

 

[merc_man]

Well now on the Stihl saws only the port width is determined by the piston skirt width, enough cylinder wall needs to be left for the piston skirt to effectively seal the port opening. Other saws may be the same but others will have wider skirts so then the 80% rule has to be followed, that`s 80% of the cylinders width measured on the cylinder surface. I widen both intake and exhaust ports. What affects RPM the most is raising the exhaust port roof increases RPM but loses torque, gaining a bit by lowering the jug will give a bit of extra torque without affecting the RPM much. Running one ring will increase RPM somewhat due to less drag, jury is out on if one ring will last as long as two and make the same compression.

So if you deck cylinder or do a gasket delete and thickness is 20 thousands of an inch that you take off. does that mean you have to raise intake and exhaust the same amount to make up for that?

Sent from my SGH-I747M using Tapatalk

 

[pioneerguy600]

So if you deck cylinder or do a gasket delete and thickness is 20 thousands of an inch that you take off. does that mean you have to raise intake and exhaust the same amount to make up for that?

Sent from my SGH-I747M using Tapatalk

If you want to return the saw back to the way it was before you started. By lowering the cylinder you have done two things, increased the compression and increased the intake duration, both good things for a work saw so by just leaving the port timing alone you have made good gains. The next thing I do is extend the upper transfers over toward the intake side to get more of the incoming fuel charge to stay in the cylinder and this helps push the exhaust out.