ID cylinder.

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I was scroungeing a old repair shop the other day and saw a open port piston sticking out of a old 55 case.

I assume you mean a windowed piston for a closed port cylinder?
Terminology gets confusing with this stuff. An open port (cylinder) piston is 'closed'/non windowed, a closed port (cylinder) piston is 'open'/windowed...
 
Not sure of your direction on this with the reference to 'finger ports' but just to be clear we're not talking open port vs closed port here.
Factory bottom fed design on closed port transfers has been common practice on many models of very high revving/high output saws, more particularly with quad ports but there are also many examples done in dual port configs. Some were even factory recommended 'performance upgrades' that were implemented by dealers on new saws.
This is nothing new...

I don't see this as something that would significantly move the peak torque down in the revs, though that it adds a bit more crank case volume may have that effect to a degree.
You could also look at this mod as feeding the lower transfer in a more direct/uninterrupted path rather than having to convolute in from the side through the piston windows. Six 'o one, half doz 'o the other...
Yes there are some new flow dynamics but the entry and exit angles of the uppers remain largely unchanged.
You flatter me with your suggestion that there may actually be a direction to my spontaneous analytical musings. :surprised3:

Finger ports.
My introduction to chainsaw engines was entirely through the window of Husqvarna's Australian 1983 model range. As an EMAB subsidiary, more brands kept appearing on our sales & service inventory. First Partner, then Poulan & Pioneer came on board, each expanding my knowledge of the diversity of design concepts.
It was Kevin Murray, then Pioneer's design engineer, who used the term "finger ports" to describe right-angled ports cast into the cylinder sides and rear by means of retractable "fingers" on both the inner dolly and the outer mould from beneath the cylinder base.
This is not the same as sand cast bottom fed quad or dual ports found on Husky 480, 372, etc.
as you describe, so I agree with your first paragraph.

Re your second paragraph. On reflection, I was probably trying too hard to find an explanation for the subjective impression that the non-original piston saw performed better, when in all likelihood, no definable explanation exists.
 
I assume you mean a windowed piston for a closed port cylinder?
Terminology gets confusing with this stuff. An open port (cylinder) piston is 'closed'/non windowed, a closed port (cylinder) piston is 'open'/windowed...
I did say that backwards. The piston is a windowed piston and my cyl are closed port.. I wrote that as I was waiting on the birth of my new granddaugther yesterday. 7lbs 15 oz. And forgive me, I am just looking for a way to fit her birth into a conversation. :numberone:
 
Thankyou, Yes this is my first great grandbaby. My grand daughter, the baby's mother, is 21yr old and her first. Her brother was there with his girl friend and I told them if they got busy we could have another in about 9 months. I also have two step great grandkids, both boys. Their dad is in the Navy and stationed in Jacksonville fla so we dont get to see them as often. The youngest is 3 and has had a heart transplant, so they dont get to come up and visit much as they sort of have to stay close to their heart doctor.
 
Thankyou, Yes this is my first great grandbaby. My grand daughter, the baby's mother, is 21yr old and her first. Her brother was there with his girl friend and I told them if they got busy we could have another in about 9 months. I also have two step great grandkids, both boys. Their dad is in the Navy and stationed in Jacksonville fla so we dont get to see them as often. The youngest is 3 and has had a heart transplant, so they dont get to come up and visit much as they sort of have to stay close to their heart doctor.
My granddaughters are 20 and 15, but Greatgrandkids aren’t in the pic, yet.
 
Found the old piston, ring was froze at the front near the muffler port.
I got it off but just as I thought it was going to slip off the piston it broke.
I was able to clean up the ring groove so the pice of ring i used fit fine.
Also cleaned most of the scuff off the piston so think I am just going to buy a ring for this saw and get it running for the fellow who brought the box to me.

Think this is the correct piston ring.
https://www.jackssmallengines.com/Products/Castor/Pistons-And-Rings/Piston-Rings

:D Al
 
never heard of castor rings, guessing its a knock off of caber. for the few extra dollars id go with a caber but to each their own.
I think it's a Castor ring for a Caster trimmer, which just happens to fit the other pistons.

I'm told that a 45mm x 1.5mm ring for a 154 /254 will work but I haven't tried it myself.
 
The story I was told was the saw was some how ran lean. when they took the carb off and apart it was full of fine saw dust where the diaphran is.

That is what it looked like to me also lean condition or a quick straight gas.

haven't seen a caber ring sourse for the 45mm. x 1.5mm

:D Al
 

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