Saw builds

[jmssaws]

I'd like to understand durations and what that all means to a 2 stroke. I'll start a thread for that.
So Shawn, what is your take on case capacity and velocity? Lots of talk of it making power and the need to keep the case as tight as possible. But at least on the 066 it seems that it's irrelevant.


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It makes more sense to use duration instead of openings but I learned degrees and it's hard to switch.

 

[junkman]

I don't know if a all oem parts 066 can be made to beat a 394. I haven't done it anyway

That;s why they say Husky for racing ,Stihl for working .

I'd like to understand durations and what that all means to a 2 stroke. I'll start a thread for that.
So Shawn, what is your take on case capacity and velocity? Lots of talk of it making power and the need to keep the case as tight as possible. But at least on the 066 it seems that it's irrelevant.


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I am no builder ,but my take is a bigger case holds the air in longer ,making tourque ,a smaller case lets the air out faster making more hp ?

 

[srcarr52]

I'd like to understand durations and what that all means to a 2 stroke. I'll start a thread for that.
So Shawn, what is your take on case capacity and velocity? Lots of talk of it making power and the need to keep the case as tight as possible. But at least on the 066 it seems that it's irrelevant.


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You have to match the transfers and blowdown to the case compression. Often people open up the intake too much and kill case compression and then they can't take advantage of larger transfer ports.

 

[srcarr52]

It makes more sense to use duration instead of openings but I learned degrees and it's hard to switch.

Duration makes more sense to me, larger number = larger time open.
Openings are counter intuitive and inconsistent, larger number on ex or trans = less time open, larger number on intake = longer time open.

 

[Mattyo]

ah... now I gots a coke can trick for putting seals in w/o worrying about inversion

 

[paragonbuilder]

You have to match the transfers and blowdown to the case compression. Often people open up the intake too much and kill case compression and then they can't take advantage of larger transfer ports.

How is this determined? Does capacity need to be measured and factored in?


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[drf256]

How is this determined? Does capacity need to be measured and factored in?


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Think it all has to be factored in. 40* of case compression is nice, I personally tailor it from there.

 

[paragonbuilder]

Duration makes more sense to me, larger number = larger time open.
Openings are counter intuitive and inconsistent, larger number on ex or trans = less time open, larger number on intake = longer time open.

I haven't fully wrapped my head around opening timing so maybe it will be easier to start with duration for me.


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[paragonbuilder]

ah... now I gots a coke can trick for putting seals in w/o worrying about inversion

You going to share Matty?


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[paragonbuilder]

Think it all has to be factored in. 40* of case compression is nice, I personally tailor it from there.

How is the 40* measured?


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[huskihl]

How is the 40* measured?


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Piston is on its way down. Intake is closing off. From the time the skirt closes the intake, the case is gaining compression. Then the upper transfers open and release the charge up on top of the piston. 40° refers to intake closing at 80° atdc, and upper transfers opening at 120°atdc

 

[mdavlee]

What saws have you gone there with Mike?


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Solo, dolmar, 1122, 372xpw

 

[paragonbuilder]

Piston is on its way down. Intake is closing off. From the time the skirt closes the intake, the case is gaining compression. Then the upper transfers open and release the charge up on top of the piston. 40° refers to intake closing at 80° atdc, and upper transfers opening at 120°atdc

Ahh. Great thank you Kevin.
And I also hear of case compression angle. What is this?


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[huskihl]

Ahh. Great thank you Jon.
And I also hear of case compression angle. What is this?


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Uhhh. He's huskstihl. Jon ain't around here much. I'm Kevin.

Haven't heard that term used. "Rod angle" is a term that refers to piston speed or movement per degree of crank rotation. At 0°, or tdc, 5° of rotation moves the piston very little because the rod is pointing straight up the bore. At 90° atdc, 5° of crank rotation results in more piston travel and speed

 

[paragonbuilder]

Uhhh. He's huskstihl. Jon ain't around here much. I'm Kevin.

Haven't heard that term used. "Rod angle" is a term that refers to piston speed or movement per degree of crank rotation. At 0°, or tdc, 5° of rotation moves the piston very little because the rod is pointing straight up the bore. At 90° atdc, 5° of crank rotation results in more piston travel and speed

My apologies Kevin. I try hard to keep it all straight.
I'll look for where it was mentioned. I think it was @Mastermind


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[paragonbuilder]

Here is the one I was thinking of.

I feel so dirty now......


I went over to AS and found my 262 thread..

"OK, I've checked the timing numbers. Stock Mahle jug, with a base gasket.

EX: 103.5
TR: 116
IN: 69

That means we have only 12.5 degrees of blowdown. Cool huh?

Case compression angle is 47 degrees.

No wonder these saws are factory hotrods."

The one jug I posted about was the one with the highest transfers.

I remember checking several more after that.......

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[paragonbuilder]

I guess it the same thing looking at the numbers he posted...


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[Tor R]

Here is the one I was thinking of.

far as I remember those timings (IN 69, TR 116, EX 103.5°) where on some of the Mahle jugs, but if I got my timings correct KS jugs has different TR numbers, and a few years of Mahles had pretty much same timings as KS.

 

[jmssaws]

This is getting good let's keep it going

 

[jmssaws]

I am very interested in modding a wj carb,I really want to know how to make a stock carb produce more power.

Anybody had any luck with the wj carbs?