026/260 finger ports questions

[Ketchup]

Hi Guys
I’m porting an 026 for fun and thought I would try some finger ports. My plan is a tight squish (0.018”), wide exhaust (maxed out but not raised much), “Mushroom” Muffler, light intake widening (shooting for 74-75 degrees opening) and lower transfer cleanup. Sounds like people do fingers but I couldn’t find specific info.

So:
Should I end the fingers above or below the mains? Stock Blowdown is 24 degrees. I feel like I could raise the uppers a bit and shorten the blowdown.

Is my exhaust plan excessive? Will it affect transfer velocity?

Is there a piston I could swap in with a centered single ring? Especially with a slightly longer skirt?

Does a bigger carb help with the added transfer?

The saw is fugly, so no concerns about hacking it up.

Any thoughts or info is appreciated!

 

[huskihl]

You’d have to run the piston backwards or use a different one. The ring ends will snag on the fingers.

 

[Ketchup]

You’d have to run the piston backwards or use a different one. The ring ends will snag on the fingers.

Hmm. My rough original measurements indicated enough room for a thin finger port beside the ring ends. Maybe I was optimistic?

I read this:
http://opeforum.com/threads/fitting-a-husqvarna-246-piston-to-a-stihl-026.1971/page-3

Which is discouraging. Headed out to flip the piston and check my original measurements.

 

[Lightning Performance]

Get a bigger jug like an 028S. You can flip that piston around and have some room for finger ports. Doc makes them go with machine work and lots of transfer work. Tiny jug. No room for mistakes on 026's.

 

[Agent Smith]

Get a bigger jug like an 028S. You can flip that piston around and have some room for finger ports. Doc makes them go with machine work and lots of transfer work. Tiny jug. No room for mistakes on 026's.

028s jug on an 026?
Never heard of such things

 

[drf256]

Hi Guys
I’m porting an 026 for fun and thought I would try some finger ports. My plan is a tight squish (0.018”), wide exhaust (maxed out but not raised much), “Mushroom” Muffler, light intake widening (shooting for 74-75 degrees opening) and lower transfer cleanup. Sounds like people do fingers but I couldn’t find specific info.

So:
Should I end the fingers above or below the mains? Stock Blowdown is 24 degrees. I feel like I could raise the uppers a bit and shorten the blowdown.

Is my exhaust plan excessive? Will it affect transfer velocity?

Is there a piston I could swap in with a centered single ring? Especially with a slightly longer skirt?

Does a bigger carb help with the added transfer?

The saw is fugly, so no concerns about hacking it up.

Any thoughts or info is appreciated!

You can do fingers if you add a 246 slug. Requires a lot of work, such as relieving the skirt on a lathe, Machining the pin bosses inside to clear the larger 026 small rod end, cutting the chamber flat and cutting the base around .075 to hit squish.

You’d have to run the piston backwards or use a different one. The ring ends will snag on the fingers.

Eggzachary

028s jug on an 026?
Never heard of such things

Won’t work for many reasons. Base the same. Tunnels too wide and timing all over the place. I beheaded one and lost interest. Got somewhere close to getting done then lost interest.

If you’re just playing, you can try by all means. If it’s a hopped up worker saw, I wouldn’t.

 

[drf256]

http://opeforum.com/threads/duane-pa-026.12788/

This will answer some questions.

 

[Al Smith]

Everybody has a opinion on things and this is mine .I've never finger ported anything for fear of snagging a ring .Rather than I used sweeps on the uppers with a cut domed piston .The idea is to purge the area above the intake port of exhaust fumes .It's all an option of choice which method or any others to use for that matter .They all work .

 

[huskihl]

You can do fingers if you add a 246 slug. Requires a lot of work, such as relieving the skirt on a lathe, Machining the pin bosses inside to clear the larger 026 small rod end, cutting the chamber flat and cutting the base around .075 to hit squish.



Eggzachary



Won’t work for many reasons. Base the same. Tunnels too wide and timing all over the place. I beheaded one and lost interest. Got somewhere close to getting done then lost interest.

If you’re just playing, you can try by all means. If it’s a hopped up worker saw, I wouldn’t.

I used a 246 piston in one. I ended up needing to find a jug with a thicker base on it. I don’t believe it was much thicker, but it was enough to make the difference.

 

[Lightning Performance]

Really thought that would work Doc. Maybe you have to have a pipe to hit the numbers it provides... was my thought. It would need a head. Big bore short stroke
Never considered the timing to start with. Reconsidered till you finish yours plus....I don't have a lathe and have to send out base cuts

 

[David Young]

You could go this route. Build kept the piston domed. Many ways to skin the cat. All that matters is that skin is no longer on the cat.

 

[Ketchup]

@huskihl, I flipped the piston. Looks like everything will run safely if I don’t widen my exhaust too much. Good advice there. Thanks!

@drf256, your threads are fantastic. That really answered a lot. Thanks a million for writing all that up!
It did get me going on some other questions related to the carb. I’m not clear what the epoxied carb plate is for on the HD14. Also wasn’t clear what the final solution was for the HD14. Was it ultimately a coil problem?
Deets’s WJ69 with epoxied venturi was also very interesting.

Everybody has a opinion on things and this is mine .I've never finger ported anything for fear of snagging a ring .Rather than I used sweeps on the uppers with a cut domed piston .The idea is to purge the area above the intake port of exhaust fumes .It's all an option of choice which method or any others to use for that matter .They all work .

Not sure what you mean by “sweeps” and “cut domed piston”. Are you slotting the top of the piston for earlier transfer opening and ramping the uppers so they open earlier on the intake side? Clearing the intake side of spent fumes is exactly what I’m after.


@David Young, I wish I knew what your photo was showing me. It looks like a second set of transfer uppers stretched towards the intake?

Keep the thoughts and info coming! Fun stuff!

 

[Al Smith]

Sweeps are elongations on the top of the transfers designed to direct the flow towards the area above the intake port. Cut domed and pop up are one in the same .
In my way of thinking which I'm sure not everybody agrees with is with combination of the dome and the sweeps it should improve the flow to purge the area above the intake port of residual exhaust fumes .All I can say is it must work .

 

[huskihl]

I flipped the piston. Looks like everything will run safely if I don’t widen my exhaust too much. Good advice there. Thanks!

Shartcan the bottom ring and you’ll feel a little safer about widening the exhaust on that side at least. Seeing that ring there on the recoil side of most of the new stihls kinda makes me flinch. Not a fan

 

[drf256]

@huskihl, I flipped the piston. Looks like everything will run safely if I don’t widen my exhaust too much. Good advice there. Thanks!

@drf256, your threads are fantastic. That really answered a lot. Thanks a million for writing all that up!
It did get me going on some other questions related to the carb. I’m not clear what the epoxied carb plate is for on the HD14. Also wasn’t clear what the final solution was for the HD14. Was it ultimately a coil problem?
Deets’s WJ69 with epoxied venturi was also very interesting.



Not sure what you mean by “sweeps” and “cut domed piston”. Are you slotting the top of the piston for earlier transfer opening and ramping the uppers so they open earlier on the intake side? Clearing the intake side of spent fumes is exactly what I’m after.


@David Young, I wish I knew what your photo was showing me. It looks like a second set of transfer uppers stretched towards the intake?

Keep the thoughts and info coming! Fun stuff!

Carb metering plate was epoxied. The compensating horn won’t fit in the airbox of an 026. Some older HD carbs and I believe most Zama don’t have the plate. I do the same on 036/360 carbs if one wants to use the old style metal oem filter.

There was no absolute final solution on the HD14. The carb is just too large to have normal manners. Runs well at high rpm but for firewood cutting, the 194 wins. I think @Duane(Pa) still uses it both ways. I kept drilling the jet until it was right. I learned a lot from it. I’d imagine a saw that pulled less air to need a smaller jet-it was exactly the opposite of that, the Venturi signal was less.

I would try an HD off a 361 next, because it’s one of the only HD’s with a smaller bore. Might be just right for a hot 026. Would have to plug the front impulse plate and add a standard HD pump plate.

For an attempt at a racer, I’d try an HD carb again. But I say attempt because there are just better options for racing, like the 346 or a 261 standard carb.

I still love a good 026 for actual work. They are tiny, light and have great balance with a 16” bar.

 

[Al Smith]

I've seen some modified Stihl 026's that could really get with it .I was never successful in finding one for a reasonable price to tinker with though .
In that size ,3 cube I worked on a J-Red 525 that I believe had some great potential .It was only one example of that model I had ever seen .
I stumbled over an 024 in the dealers dead pile that wasn't dead .Needed a carb rebuild and a muffler rework which pepped it up. Not quite an 026 but close enough to make a decent light weight for what I do .

 

[Duane(Pa)]

@huskihl, I flipped the piston. Looks like everything will run safely if I don’t widen my exhaust too much. Good advice there. Thanks!

@drf256, your threads are fantastic. That really answered a lot. Thanks a million for writing all that up!
It did get me going on some other questions related to the carb. I’m not clear what the epoxied carb plate is for on the HD14. Also wasn’t clear what the final solution was for the HD14. Was it ultimately a coil problem?
Deets’s WJ69 with epoxied venturi was also very interesting.



Not sure what you mean by “sweeps” and “cut domed piston”. Are you slotting the top of the piston for earlier transfer opening and ramping the uppers so they open earlier on the intake side? Clearing the intake side of spent fumes is exactly what I’m after.


@David Young, I wish I knew what your photo was showing me. It looks like a second set of transfer uppers stretched towards the intake?

Keep the thoughts and info coming! Fun stuff!

Doc sent a blue Ducati coil with the saw. I swapped it out (installed it) and life got better. I’m thankful Al thought enough of me to keep working on the many obstacles he encountered. I have a pile of saws, most just sit because I grab this one almost every time. It pulls 3/8 square just fine, but there is a certain “buzz factor” with 325 that I really like and keep playing with.

 

[Erik Markussen]

Carb metering plate was epoxied. The compensating horn won’t fit in the airbox of an 026. Some older HD carbs and I believe most Zama don’t have the plate. I do the same on 036/360 carbs if one wants to use the old style metal oem filter.

There was no absolute final solution on the HD14. The carb is just too large to have normal manners. Runs well at high rpm but for firewood cutting, the 194 wins. I think @Duane(Pa) still uses it both ways. I kept drilling the jet until it was right. I learned a lot from it. I’d imagine a saw that pulled less air to need a smaller jet-it was exactly the opposite of that, the Venturi signal was less.

I would try an HD off a 361 next, because it’s one of the only HD’s with a smaller bore. Might be just right for a hot 026. Would have to plug the front impulse plate and add a standard HD pump plate.

For an attempt at a racer, I’d try an HD carb again. But I say attempt because there are just better options for racing, like the 346 or a 261 standard carb.

I still love a good 026 for actual work. They are tiny, light and have great balance with a 16” bar.

drf256, may I ask a little more about carbs for the 026. I have 026 mofo with a 194 carb, but would like to play a little more with this saw. As seen in another post, I have modified the intake and run with a velocity stack and a Uni foam filter. I don't use the saw for work, only for cutting cookies. What carb would you recommend to try on the 026, the 261 standard ? or something else.
The latest chain/bar combination I have tryed is, Stihl's new .325 NK .050 on a 16" SugiHara bar and 8 theet drive sprocket. I have also tryed 3/8 chain/bar combination, but think I prefer the .325

 

[Ketchup]

FWIW, my race friends claim 3/8lp is faster than .325.

 

[drf256]

drf256, may I ask a little more about carbs for the 026. I have 026 mofo with a 194 carb, but would like to play a little more with this saw. As seen in another post, I have modified the intake and run with a velocity stack and a Uni foam filter. I don't use the saw for work, only for cutting cookies. What carb would you recommend to try on the 026, the 261 standard ? or something else.
The latest chain/bar combination I have tryed is, Stihl's new .325 NK .050 on a 16" SugiHara bar and 8 theet drive sprocket. I have also tryed 3/8 chain/bar combination, but think I prefer the .325

I am sorry for the late response. I am just seeing this for the first time.

If you are just cutting cookies you can try an 044 carb setup. Take a look at the thread above.

I am quite happy that you like the saw so much. Your carb elbow is a work of art. The 044 carb would require a bigger entry from the elbow and a boot swap.

PM me if you need anything for the saw, or want another.

They really don’t run well with any other carb than the 194, unless it’s race only.