Part Two: The Intake Port

[Stump Shot]

The intake just double your number. 80 + 80 = 160 duration
For the exhaust and transfer double the number and subtract from 360. 100 + 100 = 200 from 360 = 160 duration, 120 + 120 = 240 from 360 = 120 duration.
You can set your wheel to zero where the port opens and until it closes is your duration.

 

[Stump Shot]

IMO, longer intake duration just kills crankcase compress and makes for a lazy saw.

There's always a line to cross and the line can move coupled with other works performed. Not easy for a new person to know, some will creep to it and others will jump past the finish line depending on their style. Either way will take a bunch of saws under ones belt to get to the sweet spot.

 

[Ronie]

The intake just double your number. 80 + 80 = 160 duration
For the exhaust and transfer double the number and subtract from 360. 100 + 100 = 200 from 360 = 160 duration, 120 + 120 = 240 from 360 = 120 duration.
You can set your wheel to zero where the port opens and until it closes is your duration.

Thanks, that's easier to remember than the way I was trying to do it.

 

[JohnnyBlade]

There's always a line to cross and the line can move coupled with other works performed. Not easy for a new person to know, some will creep to it and others will jump past the finish line depending on their style. Either way will take a bunch of saws under ones belt to get to the sweet spot.

Ed Zachary. I dont know which way id go with the new info learned but its a piece of the puzzle i feel i needed to know. May help things along, may put new questions in my head. Thats what makes deez garden tools so damn addictive

 

[Stump Shot]

Ed Zachary. I dont know which way id go with the new info learned but its a piece of the puzzle i feel i needed to know. May help things along, may put new questions in my head. Thats what makes deez garden tools so damn addictive

Just keep plugging away at it, and keep good notes on each one you do.

 

[JohnnyBlade]

Just keep plugging away at it, and keep good notes on each one you do.

Im trying. Notes r sooo important. Ive only gone backwards on 2 saw so far.
Cs490. We wont even get started. A few know about it

And a husky 61. And funny thing that was said today from Scarr is what i did. Lowered the intake too much and it is a total turd.

So the pieces r going together in baby steps. Rome wasnt built in a day.
Thanks for the words of encouragement!

 

[Ronie]

Im trying. Notes r sooo important. Ive only gone backwards on 2 saw so far.
Cs490. We wont even get started. A few know about it

And a husky 61. And funny thing that was said today from Scarr is what i did. Lowered the intake too much and it is a total turd.

So the pieces r going together in baby steps. Rome wasnt built in a day.
Thanks for the words of encouragement!

I lowered the intake to much on a 372 and using JB Weld was suggested, it worked great to raise the floor to where I needed it to be.

 

[Lightning Performance]

I'd say Shaun is right on. Anything less than thirty eight in the secondary is just sluggish most times on work saws. I've seen thirty five work well racing but never with a long bar. Betting most of the long bar runners are near forty. Considering thirty eight to forty two in the bottom end for stroke with good crisp snap. Forty with forty works and more numbers like eighty, one twenty and one hundred keep showing up as productive and well mannered most times imo. Intakes too far are messy and make for nasty filters from spit back while working. Randall knows them all within a few degrees and how they react to changes with it, I'm sure. I just do Stihls mostly.

Any new threads on the saw series?

 

[JohnnyBlade]

I lowered the intake to much on a 372 and using JB Weld was suggested, it worked great to raise the floor to where I needed it to be.

Yup. Thats what i was gonna do. If my memory serves me correctly stock it sat somewhere around 72 on the 61. I didnt wanna go that far, maybe to 75-76. On my other shoulder i think i was swayed to 80. Wound up at 81 i think. Total turd. Ran fine but ..... what i have learned is less is more 90% of the time. And if u think its too much it probably is. Lucky i have a PHD in JB welding. The 61 will make it back to the bench eventually.

 

[Ketchup]

How do you guys feel about having a part 8 for strato specific porting? Some people say they port the same way as other saws, but I disagree. Talking strato always gets mucked up with earlier generations of non-strato. These threads are amazing, but they bounce all over the place and stratos are always just mentioned, not focused on.

I‘m raising the question here because the main difference in a strato is the intake side. But they run different carbs, have different timing, and respond to port work slightly differently.

Considering the number of new saws that are stratified, I want a special place to talk about them. What do you guys think?

 

[Mastermind]

How do you guys feel about having a part 8 for strato specific porting? Some people say they port the same way as other saws, but I disagree. Talking strato always gets mucked up with earlier generations of non-strato. These threads are amazing, but they bounce all over the place and stratos are always just mentioned, not focused on.

I‘m raising the question here because the main difference in a strato is the intake side. But they run different carbs, have different timing, and respond to port work slightly differently.

Considering the number of new saws that are stratified, I want a special place to talk about them. What do you guys think?

Carry on.

 

[Terry Syd]

I‘m raising the question here because the main difference in a strato is the intake side. But they run different carbs, have different timing, and respond to port work slightly differently.

Here's my 'rule of thumb' for a strato - match the strato and intake timing. If you need a bit more timing, then do BOTH of them.

The hardest thing to get into the engine is the AIR. Tweaking the carb needle will get you all the extra fuel you need, but you have to have the air to burn it.

If you make either the intake or strato port timing shorter, then you are only 'shortchanging' the intake stroke.

 

[Ketchup]

Here's my 'rule of thumb' for a strato - match the strato and intake timing. If you need a bit more timing, then do BOTH of them.

The hardest thing to get into the engine is the AIR. Tweaking the carb needle will get you all the extra fuel you need, but you have to have the air to burn it.

If you make either the intake or strato port timing shorter, then you are only 'shortchanging' the intake stroke.

https://opeforum.com/threads/part-8-the-stratified-chainsaw.23462/

I tried to @mention you, but it wouldn’t work.

 

[Thesandman]

I have a old Pulaan 4000 ex 98.5, trans 124.5 and int 65*btc. The int. Port is short tube.750id x 1.05 that dumps into plenum area appx 1.02w x .650h x .650 deep with port window .450 x 1" with a divider bar. Another problem is the tube dumps into left side of plenum area. My concern is that the chamber area is killing int. velocity. The port window is about same area as tube. I'm wondering if the chamber is to resonate a higher pressure till intake opens again? Saw was designed around 8500 rpm. Is chamber(plenum) hurting velocity at 9 to 9500 in cut? PS. Ex window is .45 x 1.17 oval.

 

[Ketchup]

I have a old Pulaan 4000 ex 98.5, trans 124.5 and int 65*btc. The int. Port is short tube.750id x 1.05 that dumps into plenum area appx 1.02w x .650h x .650 deep with port window .450 x 1" with a divider bar. Another problem is the tube dumps into left side of plenum area. My concern is that the chamber area is killing int. velocity. The port window is about same area as tube. I'm wondering if the chamber is to resonate a higher pressure till intake opens again? Saw was designed around 8500 rpm. Is chamber(plenum) hurting velocity at 9 to 9500 in cut? PS. Ex window is .45 x 1.17 oval.

I’m sure the intake shape doesn’t help, but I would be more suspicious of the high intake.

 

[Thesandman]

Hey Brother Ketchup; By high do you mean the 65*btc opening? Thanks

 

[Ketchup]

Yep. I’m guessing, but I think it would run better at 70-72BTDC.

 

[Thesandman]

Yes I'm thinking when I cut base to add compression int will move that way and ex will move to a more favorable number also.

 

[Ketchup]

Yes I'm thinking when I cut base to add compression int will move that way and ex will move to a more favorable number also.

It should. Raising the transfers closer to 20 degrees blowdown might help as well.

Any pictures of that intake layout?

 

[Thesandman]

I just found out this cylinder is a copy of early 70,s homelite. Almost exactly but homelite had reeds