Part Three: The Transfer Ports

[huskihl]

I’ve tried the top 266 style and compared it to the bottom one with windows. The bottom one runs much better. The added full skirt on the top piston disrupts flow into the lower transfers.

Like Steve mentioned, the middle one is for the open port non xp 268.

 

[smokey7]

I do the same thing with the 48mm jugs like the jonny 630 husky 162 they get a windowed husky 61 piston. Much more sporty runner with that not alone.

 

[Stump Shot]

I think it was @sunfish that turned me on to the full windowed piston for the 266. I see no reason that shouldn't work with any saw motor that has closed port transfers and full circle window pistons.

 

[Ketchup]

How about wash pattern on the piston crown? How much do you read from it and what do you do when it doesn’t look right?

Does anybody aim their uppers differently for a popup?

 

[Ketchup]

 

[wcorey]

Assuming I can get a wash pattern that's readable at all, typically all I expect to see that has practical use for me is whether the transfers are balanced side to side. I guess another thing would be signs of possible short circuiting.
I'm sure there are other things to be read but I'm not sure I'd know what to actually do about it.

 

[mdavlee]

How about wash pattern on the piston crown? How much do you read from it and what do you do when it doesn’t look right?

Does anybody aim their uppers differently for a popup?

Entry angle is important. A pop up can make them have a small disturbance if it’s tall and not tapered at all. I never changed how I did the uppers for a flat top over a pop up though.

 

[pbillyi69]

i have read in progression up to this point in the whoke thread, because i want to try my hand at porting one of my saws and really want to make a piped and ported saw. as i read this stuff and begin to wrap my head around all of the factors that are considered in making a good runner I am so gratefull to all of you guys that have shared your experience and knowledge. I am not a dummy by any means but wow am I an infiant in the knowledge that I thought i knew. Thank you for letting me learn

 

[Nutball]

Are the lower transfers in most pre xx1 or 5xx series saws too big, too small, or just right? Echo, and some others like Poulan are known to use transfer stuffers. Why not make it right the first time around? Anyway, I feel like the lowers on the old 028 and 038 are pretty big, and could benefit from some stuffing.

Now that I think of it, maybe my ms250 would benefit from lots of stuffing. What think the smart fellers?

 

[Ketchup]

I think most stuffers are in there to increase transfer velocity. Some of the Echo stuffers may be trying to effect scavenging patterns. I think the danger of stuffers is loss of volume.

I haven’t seen that many saws with transfer stuffers, but the ones I have seen usually have relatively tight case volume.

 

[Nutball]

but the ones I have seen usually have relatively tight case volume.

Sounds like less of a need for them.

I think I mostly have case volume in mind when it comes to stuffing the transfers. I have read of others avoiding much hogging on the lowers and tunnels for the sake of case volume.

I'm gonna do it: fill the lowers on a 028 & ms250... And I'll post pics... unlike some people.

 

[Maintenance Chief]

Ive got a couple McCulloch 10-10 cylinders to work with putting together a parts saw, 1 is a .030 over bore.
What I'm looking at is basically groves sliced into the sides of the bore, from what I gather if I widen the bottom of the ports for the piston to scoop up some more mix to push to the combustion chamber I'm not going to gain anything?
But when I look at a 10-10s cylinder its just a big square pocket and I was thinking about recreating that in the 10-10 cylinder.
Obviously a clamshell design so a little limited in changes.

 

[Nutball]

 

[Ketchup]

View attachment 278712 View attachment 278713
View attachment 278753

What do you think? Did you see gains?

 

[Ketchup]

Going back a bit here.

How much do you guys think transfer uppers flow after BDC? Any? Perhaps flow timing is longer on quad transfers. We know on stratos that they switch direction somewhere before intake begins.

So from roughly 20 degrees BBDC to 95 degrees ABDC, what’s going on in there?

Which way is charge moving and when?

Does a piston wall or crank weight closing a lower have any effect? What kind of timing does the crank weight have front and back?

How much charge is pulled back into the uppers?

What is happening around the time the uppers close?

How significant is the vacuum generated between transfer close and intake opening?

Obviously it’s important for stratos. How important is it for general intake vacuum?

Does shorter timing between transfer upper close and intake opening effect spitback?

Can it make a sluggish intake?

...

Sorry. Too much coffee.

 

[Nutball]

What do you think? Did you see gains?

I finally started grinding on it today. Roughed in. My hands are tired since I haven't grinded for a while.

 

[Terry Syd]

How much do you guys think transfer uppers flow after BDC? Any?

Here's the answers to all your questions. -
https://b-ok.global/book/977875/b0a20d?regionChanged=&redirect=163474285
Forget the math, just concentrate on the text and the graphs. The math is for the designers, you just want to understand the concepts. The engine called 'Loop saw' is a Stihl chainsaw.

 

[Moparmyway]

 

[afleetcommand]

Long thread fun stuff. Just curious was any discussion about the angle of the "roof" or top of the transfers , not on the "x y" plane but "z" ? Also differential height transfers on those quad port cylinders with possibly the "exhaust" side leading by a few degrees? I got into a few pages...my short term memory is shot so five pages in I already forgot what was on the first page. Also the impact of grinding the lowers and adding x-section on the intake as in enters the crank case on case volume & intake charge velocity/pulse upstream through the air box. Just curious where everyone ended up.

And while "theory" is behind designs. Always curious on the thoughts on surface finish. AND curious on what folks are thinking about why the new saws love to wrap the transfers around the exhaust port

 

[Moparmyway]

To me, it depends on what saw we’re talking about.

066/660 is much different than the 084/088, and then there’s the 880. Or is it the 084, and then the 088/880.

See what I did there ?