Jonsered 2165 build

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I got the 268 piston today, I would really appreciate any suggestions on how to bring the rpm up without losing torque. As it stands now with the 266 piston my numbers are:
Squish .022
Intake 83
Exhaust 100
Transfers 126
 
I had forgotten that a very knowledgeable member had given me some numbers to try in another thread and I'm going to try those out and will post the results. The saw runs good the way it is but I'm hoping that I can get some more out of it. I'm shooting for these numbers:
Intake 80
Exhaust 100
Transfers 120
 
I got the 268 piston today, I would really appreciate any suggestions on how to bring the rpm up without losing torque. As it stands now with the 266 piston my numbers are:
Squish .022
Intake 83
Exhaust 100
Transfers 126

Toss the windowed pistons in the trash is how I gained torque back. I never liked them in a 372 style jug. Raising the transfers will help from where you’re at right now
 
Toss the windowed pistons in the trash is how I gained torque back. I never liked them in a 372 style jug. Raising the transfers will help from where you’re at right now
Thanks for the advice, I'm going to give it one more try and if it doesn't work out I'll just go back to a 372 piston. At least when someone is contemplating using the 266 or 268 piston they can see how it turned out for me.
 
Thanks for the advice, I'm going to give it one more try and if it doesn't work out I'll just go back to a 372 piston. At least when someone is contemplating using the 266 or 268 piston they can see how it turned out for me.

To take advantage of the windows you need to raise the lowers way up. If not you’re dead heading flow of the air right into the wall above the lower transfer openings. Think of the piston as a cup upside down in a pan of water.
 
To take advantage of the windows you need to raise the lowers way up. If not you’re dead heading flow of the air right into the wall above the lower transfer openings. Think of the piston as a cup upside down in a pan of water.
If you take the skirts up flush with the lower entrance, is that enough?
 
If you take the skirts up flush with the lower entrance, is that enough?

The windows in the piston need to be lined up with the entrance like a 395 or Stihl jug to take full advantage. But if you do that the cylinder won’t work with a stock piston later on as good either. I tried adding windows in a stock one and a 268 piston. Neither ran as good as stock piston with lowers just raised 1/8” or less after dropping the jug with machine work.
 
To take advantage of the windows you need to raise the lowers way up. If not you’re dead heading flow of the air right into the wall above the lower transfer openings. Think of the piston as a cup upside down in a pan of water.
I'm just trying to understand, so please don't take this as if I'm arguing. If the windows are covered by the cylinder wall and won't let air flow through them wouldn't the piston be acting like the non windowed 372 piston. I understand that the windows won't provide any gain in flow, I also don't see how there would be any loss of flow verses the 372 piston. The reason I'm trying the 266 and 268 piston so I could make a pop up to bump up compression.
 
I'm just trying to understand, so please don't take this as if I'm arguing. If the windows are covered by the cylinder wall and won't let air flow through them wouldn't the piston be acting like the non windowed 372 piston. I understand that the windows won't provide any gain in flow, I also don't see how there would be any loss of flow verses the 372 piston. The reason I'm trying the 266 and 268 piston so I could make a pop up to bump up compression.

The piston isn’t full circle so you’re losing the flow into the cylinder walls. Push each piston down into a large glass and watch the water flow
 
Well I've been talking with some people with a lot more knowledge about these things than me and have come to the conclusion that I'm wasting my time with the 266 and 268 piston. I'm going to send the 268 piston back and get a 372 piston. As it is now the saw runs good and has good torque but didn't turn out like I wanted. I'm going to try and get close to the timing numbers I was given and hopefully have a little faster and stronger saw than stock.
 
Update: I tried to bring the transfers up with a ball burr and it got away from me and took the plating off between the transfers, glad I didn't pay much for the cylinder. So I only had two options, put on a new oem cylinder or put on a big bore cylinder I have. I'm saving the new cylinder until I get better at porting so it's the BB. I cut the base, widened the exhaust and squared up the intake, gasket matched and knife edged the lower transfers, raised the upper transfers and took a little off the intake side of the piston. The numbers are now,
Squish .017-.018
exhaust 101
intake 80
trans 121
compression 205psi
It seems to run good but didn't get a chance to do a good tune because I ran out of gas.


 

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I've ran 3 tanks through it now and it's running good, with good torque but it just don't have the high rpm I was wanting. I just don't know what changes need to be made to get the rpm up so it's going to stay like it is for now. Maybe it has to much compression? If any experienced porters have any ideas, I'm all ears.

 
That's odd. Mine ran crazy good. Gasket deleted. About the same psi you have there and squish. HyWay top end. I didn't raise the lowers much at all, just mostly blended them in nice and smooth. I did open up the intake as much as it would go, and shaped the lip a bit to dump down into the chassis. I forget which carb this thing had. Exhaust super open, both at cylinder and muffler. Didn't touch the piston. Running fairly lean, but with 32:1 mix. I brought her down a few rpms after I heard how lean it was in the vid. In person the thing is so loud, it can be a bit difficult to tell. She is in freshly fallen(and tensioned) European Beech in the vid.



154599213.4aCFnmt7.jpg


Thats a Mercury gauge without a hose. So it usually reads 5-10psi higher than a typical hose gaugey thang.
 
That's odd. Mine ran crazy good. Gasket deleted. About the same psi you have there and squish. HyWay top end. I didn't raise the lowers much at all, just mostly blended them in nice and smooth. I did open up the intake as much as it would go, and shaped the lip a bit to dump down into the chassis. I forget which carb this thing had. Exhaust super open, both at cylinder and muffler. Didn't touch the piston. Running fairly lean, but with 32:1 mix. I brought her down a few rpms after I heard how lean it was in the vid. In person the thing is so loud, it can be a bit difficult to tell. She is in freshly fallen(and tensioned) European Beech in the vid.


That saw is running good. I don't know what I'm doing wrong but another member was kind enough to help me out and hopefully with his help I can get this figured out. I know I'm going to be working on the port shape and opening up the muffler some more.
 
That saw is running good. I don't know what I'm doing wrong but another member was kind enough to help me out and hopefully with his help I can get this figured out. I know I'm going to be working on the port shape and opening up the muffler some more.

Mine had no baffle. I opened it up similarly to my 288xp. It's ugly, but effective.

160224489.PS8JivST.jpg


I didn't need to, but maybe you need to advance the timing.
I barely mess with the lowers. I think some folks go way crazy on these for a work saw. I do almost exactly the same work Randy/Mastermind does to his. Just touch it enough to blend it in with the chassis so it all gets shot up into the uppers. I never seen any advantage in messing with the pistons, other than them being lighter:

Revisitingthe372006_zps14683bcf.jpg
 
Thanks for the pics. I wish I had a right angle grinder to get at the upper transfers. I did raise mine with a pencil grinder and a ball burr but I can't get very far into the transfer doing it like that.
 
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