OK you porting experts...a little perspective! LOL

weimedog · January 02, 2011, 10:46:50 AM

What do you think the "blow down" numbers look like on this hot rod!

(NOS 903 Homelite) :D

Think a muffler mod would make a difference?

Where Homelite ended up...

Power...540 style

sharkey · January 02, 2011, 05:13:14 PM

Hi Weime,
From the pics, the blowdown looks low maybe 12 degrees? Does the 540 use a full skirt windowed piston?

Al_Smith · January 02, 2011, 06:50:43 PM

That top picture kind of looks like a c-5 with that open transfer .

weimedog · January 03, 2011, 09:15:22 AM

That's a 903 but I do have a NOS XP1050 and NOS Super77,770, etc Cylinder and a bunch of NOS pistons for those old gear drives kickin around..maybe I'll dig them out and shoot pics.

farley9n · January 15, 2011, 03:32:42 PM

That 540 cylinder looks more like the 8800. The 540s I have are open transfers. Either way, they are good saws!
:P .....Just looking around & learning......Bob

Well....I tried to show a picture of both side by side and all I showed was how much I still have to learn!

CX3 · January 15, 2011, 07:28:41 PM

Hey guys if one of you has extra time could you put the little "pointer fingers" on some of those pics so I could understand more of what youre talking about. I am interested but not catching the lingo. Thanks.

SwampDonkey · January 15, 2011, 07:39:54 PM

:D I don't know what the excitement is over. I didn't get that excited opening up my brush saw last spring. ;) Got another 100 acres outta her though. :D

Al_Smith · January 15, 2011, 07:52:40 PM

Quote from: CX3 on January 15, 2011, 07:28:41 PM
Hey guys if one of you has extra time could you put the little "pointer fingers" on some of those pics so I could understand more of what youre talking about. I am interested but not catching the lingo. Thanks.

I'll give you a little tutorial ..

The first picture shows what is termed "open transfers " these are most generally used with full skirted pistons .Usually although not always used on older designs .

The second picture shows tunnel designed transfer ports .As a rule they are used with either a windowed piston or a cut side skirt piston .Usually more modern saw use this type or a variation of this type transfer ports .

An interesting note on that though ,most likely the hottest little trim type saw in history,the Stihl 200T is an open transfer design .

Now historically there have been so many designs of the transfer ports of two cycle engines which are so numerious an entire portion of this forum could be filled with them .

Saw Dr. · January 15, 2011, 09:20:09 PM

Quote from: Al_Smith on January 15, 2011, 07:52:40 PM
Quote from: CX3 on January 15, 2011, 07:28:41 PM
Hey guys if one of you has extra time could you put the little "pointer fingers" on some of those pics so I could understand more of what youre talking about. I am interested but not catching the lingo. Thanks.
I'll give you a little tutorial ..

The first picture shows what is termed "open transfers " these are most generally used with full skirted pistons .Usually although not always used on older designs .

The second picture shows tunnel designed transfer ports .As a rule they are used with either a windowed piston or a cut side skirt piston .Usually more modern saw use this type or a variation of this type transfer ports .

An interesting note on that though ,most likely the hottest little trim type saw in history,the Stihl 200T is an open transfer design .

Now historically there have been so many designs of the transfer ports of two cycle engines which are so numerious an entire portion of this forum could be filled with them .

Yeah, MAC 850 is open also. Cracks me up when the "experts" start talking about how crappy open-transfer clamshell saws are. I guess most of them have never heard of an 800 series MAC, though.

Al_Smith · January 16, 2011, 05:09:02 AM

Mac 10 series porting is in a class all it's own .

You can't really call it open because bottom is closed and goes through a winow in the piston but the grooves are open to the side of the piston . By staggering the grooves in relationship to postion of the piston stroke in regards to the opening and closing of those type transfers the velocity and direction of transfer can be varied some what during the cycle .

There is some variation in design depending on weather they are early 10-10's or later like the 700's or the larger 800,sp-81 ,850 etc .

Of all the types I've ever seen these are the most unique of all .So odd that I'm at a loss as what to with them as far as engine enhancements so I just leave them alone .

In conversation with big Dave he said when he worked for Husqvarna they studied ways to improve them and gave up so I don't feel so bad .If a group of mechanical engineers couldn't get-er-done then an old grease monkey like me stands little chance . :D

weimedog · January 16, 2011, 08:34:01 AM

Quote from: farley9n on January 15, 2011, 03:32:42 PM
That 540 cylinder looks more like the 8800. The 540s I have are open transfers. Either way, they are good saws!
:P .....Just looking around & learning......Bob

Well....I tried to show a picture of both side by side and all I showed was how much I still have to learn!

You know.....you may be right on that 8800...

Its going on that 540 once the cylinder thats on there is worn...since it looks like new, that might be with a grand kid who shows interest some day in the future....for now it sits in a box right with its NOS piston.

Al_Smith · January 16, 2011, 08:47:14 AM

I've seen people cut the bottoms out of closed tunnel Stihl transfers which in essence would turn them into open transfers .I'm not so sure this is the correct approach .

However what anyone chooses to do with their equipment is none of my business so I leave it at that .

weimedog · January 16, 2011, 09:36:15 AM

The one on the left..wonder where that inspiration came from?

CX3 · January 16, 2011, 06:58:06 PM

Thanks. Its making a little more sense. Im just not familiar with 2 stroke engines and how they "really" work

HolmenTree · January 20, 2011, 10:09:17 PM

Weim those Homelites are a different breed altogether. With their reed valve induction porting can be optomized much differentily then the piston port Jonsereds.
One of my very first competition saws was a Homie Super XL 922, at the time I couldn't or didn't know how to make it run much faster from stock.

Willard

weimedog · January 21, 2011, 01:53:23 AM

Quote from: HolmenTree on January 20, 2011, 10:09:17 PM
Weim those Homelites are a different breed altogether. With their reed valve induction porting can be optomized much differentily then the piston port Jonsereds.
One of my very first competition saws was a Homie Super XL 922, at the time I couldn't or didn't know how to make it run much faster from stock.

Willard

Yes those 900 series are. Actually the one next to the J-red is an 8800 which will eventually find its way onto a 540 I have. They are a piston port design much like the Jreds. Funny how the entire industry seemed to gravitate to these different porting schemes....the 8800 and that era Jred are remarkably similar.

On the 925's I'm not certain either what to do. There is a fellow posting over at another site who actually added more transfer ports..Seems to me there is enough& man that reduces the amount of area containing the rings!. Also you would thing the reed valve would give more leeway in intake duration and port timing in general. There was a posting of an old Home race saw built on a "C' series chassis with two separate carburators on top of an enlarged reed cage....makes one wonder what might have been!

HolmenTree · January 21, 2011, 08:20:26 AM

I have a old Jonsered 111 hotsaw build writeup ,[I'll try to email it to you like I said before] The builder welded a reed valve housing to the Jonsereds cylinder and put "boost ports in the piston intake skirt. Plus a cutoff head. Very interesting writeup.

Willard.

weimedog · January 21, 2011, 09:38:14 AM

Please do! That would be really cool to see and also give inspiration to folk to try some of those concepts again. :P

wannabeonetoo · January 21, 2011, 06:50:31 PM

Quote from: weimedog on January 21, 2011, 01:53:23 AM
On the 925's I'm not certain either what to do. There is a fellow posting over at another site who actually added more transfer ports..Seems to me there is enough& man that reduces the amount of area containing the rings!. Also you would thing the reed valve would give more leeway in intake duration and port timing in general. There was a posting of an old Home race saw built on a "C' series chassis with two separate carburators on top of an enlarged reed cage....makes one wonder what might have been!

I think he is building a saw that will run on that "special" fuel

so he needs a lot more of it !

Steve