Real talk about saw porting theory (no arguments)

[EvilRoySlade]

I've read lots but don't have the opportunity to play or apply what I read. I know there are tidbits all over the place. Does anybody have interest in chatting about basics, for those that are on the fringe? I'd like to discuss why/how certain changes work or not. Things like exhaust. Seems like it tends to be chosen first and why or why not. Does anyone map the ports on paper, why? Does anyone figure port volume, not just time/area? When/why to let strato ports flow fuel also, and how much of the intake stream? Crankcase CC ratio, fuel usage etc.

Am I a socially inept nerd, yes. Can I talk pigs and cows, yes. Do I like bacon, yes. I also enjoy an intellectual technical conversation. Who's interested? I know many of you have passed my knowledge level long ago but I'm here now and you were too at one time.

 

[jake wells]

ported saws are a fad.

 

[smokey7]

I'm kinda in the same boat. My knowledge in saws is pretty small. I know and understand porting very well in sleds quads bikes and skis. But all have pipes. Saws kubda news with me as they are totally different. If very much like to slow the saw porting learning gbpace down so I can grab it better.

 

[Dub11]

Yes I do and more or less just for the understanding of it.

 

[EvilRoySlade]

So was shag carpeting!

 

[jake wells]

my knowledge of 2 cycle chainsaws are limited i mostly play with the other breed of 2 cycle products called a lawn boy.

 

[merc_man]

It would be good if someone could make a vid of porting from start to finish. Explaining as they go what numbers mean and when changed what will happen.

Sent from my SM-J320W8 using Tapatalk

 

[SOS Ridgerider]

I'm with you @EvilRoySlade
Would really like to understand it better and get to know the hows and whys.
I have a couple of saws I wouldn't mind trying my hand at. I'm not a book learner, though.

 

[EvilRoySlade]

@jake wells, I gotta pick on you. Aluminum deck mowers were a fad too! I'd be happy to find a decent green 2 smoker now days.

 

[EvilRoySlade]

The bits I've picked up, it seems everyone dictates the powerband with the exhaust timing. I know it's more in depth than that but that's my point. How can a chamber not get cut, leaving a less than desirable exhaust timing then massaging the transfers to accommodate the exhaust?

 

[jake wells]

@jake wells, I gotta pick on you. Aluminum deck mowers were a fad too! I'd be happy to find a decent green 2 smoker now days.

toro ruined a great product and toro still sucks.

 

[peter92]

It would be good if someone could make a vid of porting from start to finish. Explaining as they go what numbers mean and when changed what will happen.

Sent from my SM-J320W8 using Tapatalk

from what ive read about porting it takes awhile to perfect it , thats why people send there saws to some one like Randy , to get it done correctly , now if people start doing video,s and numbers of how the ported a saw , it could take money away from guys that make a living out of it
you can ask question about porting and get some ideas and if you have a go , only if its a little bit , and post pics , im sure you will get the advise you need to make it right , theres a lot on youtube also
im only learning myself and find the guys very helpful if i wont to have a crack at it
Peter

 

[EvilRoySlade]

I hear ya there. However Randy has publicly mentioned that honesty is a huge part of his business. Do I believe he knows what he's doing, yes. Do I believe others do as well, yes. I do not want this to be a this guy knows, that guy doesn't conversation.

It's just an engine. Invented long before any of us were born by dudes using slide rules. Casting their own cases and pistons. There have been books written about them long ago. Nothing new is happening. There are no secrets, just understanding.

My main problem, I need to degree every saw I have and document it. Why, cause I want to.

 

[Dub11]

I hear ya there. However Randy has publicly mentioned that honesty is a huge part of his business. Do I believe he knows what he's doing, yes. Do I believe others do as well, yes. I do not want this to be a this guy knows, that guy doesn't conversation.

It's just an engine. Invented long before any of us were born by dudes using slide rules. Casting their own cases and pistons. There have been books written about them long ago. Nothing new is happening. There are no secrets, just understanding.

My main problem, I need to degree every saw I have and document it. Why, cause I want to.

What will be really help full if some cannpost that 2 stroke theory bool again. And from what I have seen a person lile me can only go so.far with what I have with out cutting base and squish.

 

[wcorey]

...Things like exhaust. Seems like it tends to be chosen first and why or why not.

This subject of saw porting needs a book or three, but I'll take a shot at a couple small points in the big picture...

Even the very basics can easily become a moving target. I only get a fraction of it most of the time and have to digest the whole process in small compartmentalized increments. Just can never visualize it all in a continuous flow...

Don't always have to start your numbers with the exhaust but it's often as good a place as any.
You start with whats most important which tends to be dictated by the physical layout of what you get to start with on a given P&C and any special consideration of the particular saw.
Can decide what numbers you want then see if the cylinder will let you get there or degree it first and see where it tells you that you have to go.
Sometimes you start with setting squish, then see how much leeway is left for the exhaust. But the options for change are usually manyfold and with every change comes a chain reaction...

Assuming there's room to wiggle, lets try doing instead the intake opening first and use some common numbers.
So decide (or decided by base cutting or whatever already) the degree opening, somewhere usually 74 to 82.
Then consider getting the typically accepted 40 degrees of case compression, so need to set the upper transfer opening at a specific point to get to that.
Then how much blowdown, 2o is pretty typical.
Now when the exhaust opens is preordained by the blowdown and consequently the rest of your numbers.

That's assuming you can get that exhaust opening number after already having cut the squish band to get the typical .020", that's determined by things like how much you can drop the cylinder due to freeporting, base thickness, etc., or how much room before the ring runs out of plating at tdc, too much/too little compression, etc...

Sometimes I feel like I'm chasing my tail trying to make the numbers work...

 

[Dub11]

Ok I still have a hard time.understanding when blow down happens

 

[cease232]

What will be really help full if some cannpost that 2 stroke theory bool again. And from what I have seen a person lile me can only go so.far with what I have with out cutting base and squish.

http://www.edj.net/2stroke/jennings/2stroketunershandbook.pdf



Sent from my iPhone using Tapatalk Pro

 

[cease232]

I hear ya there. However Randy has publicly mentioned that honesty is a huge part of his business. Do I believe he knows what he's doing, yes. Do I believe others do as well, yes. I do not want this to be a this guy knows, that guy doesn't conversation.

It's just an engine. Invented long before any of us were born by dudes using slide rules. Casting their own cases and pistons. There have been books written about them long ago. Nothing new is happening. There are no secrets, just understanding.

My main problem, I need to degree every saw I have and document it. Why, cause I want to.

I keep a record of all my saws numbers, timing, squish, port width, and piston skirt relation to exhaust floor. I also save most numbers that get posted in the forums so I can refer back and compare what others are doing.


Sent from my iPhone using Tapatalk Pro

 

[Dub11]

http://www.edj.net/2stroke/jennings/2stroketunershandbook.pdf



Sent from my iPhone using Tapatalk Pro

Thank you! Would you sare your number list at some point?

 

[cease232]

Thank you! Would you sare your number list at some point?

Sure. I realized i sounded very organized but they're mostly just written on random pieces of scrap paper. I when I have time I'll sort em out and put them up. That would make a great thread.


Sent from my iPhone using Tapatalk Pro