Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Modified Ported Work or Race saws => Topic started by: awol on January 14, 2015, 06:42:39 pm
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These are a very well designed saw, and dependable in the woods, but seem to be lacking in performance. They use a full skirted piston with windows, and all transfer flow must pass through these windows, to get to mid fed lower quad transfers. The original piston is also domed. I found that a Husky 268 piston makes a good replacement, it is slab sided but not windowed, and has enough skirt length and width to allow widening of the EX port. It is also much lighter, and has a flat top, requiring a lot of squish band and combustion chamber work.
Here is the saw stock.
https://www.youtube.com/watch?v=hIIFMow_69I&feature=youtube_gdata_player
And here it is after mods with the same untouched chain.
https://www.youtube.com/watch?v=AMlxrbizvo8&feature=youtube_gdata_player
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Sounds good!!
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Thanks!
In order to help out the restricted transfers, I added fingers at the end of the bridge.
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Nice.
You have measurments of the 268 piston and 670 piston? If not I will dig later.
I know all to well about the stock video. Own a 6700. Reminds me of a husky 365 weight and handling but less power then 365.
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I have the 670 piston in the scrap bucket, I will get pics and measurements of it and post the results. I do know that the 268 piston was around .080 taller, as that is how much material I removed from the squish band. This brought compression up to 250psi, so I had to remove a little material from the combustion chamber. Comp is now 190psi after about two gallons of gas.
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Cool. Are the finger ports separate from the mains or do they connect on top?
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The fingers are connected to the intake side uppers.
I tried to attach a photo, it shows up when I look at the thread, hope everyone else can see it.
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Good deal nice work
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The fingers are connected to the intake side uppers.
I tried to attach a photo, it shows up when I look at the thread, hope everyone else can see it.
I can see them and when clicked on pic it enlarges to giant size. Like this.
http://chainsawrepair.createaforum.com/index.php?action=dlattach;topic=4526.0;attach=10906;image
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Here are the measurements of the stock Echo piston:
Pin boss width 17mm .667"
Pin diameter 12mm .472"
Comp height 22.2m .871"
Total ht. 40.4mm 1.586"
Dome ht. 2.29mm .090"
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Here are the measurements of the stock Echo piston:
Pin boss width 17mm .667"
Pin diameter 12mm .472"
Comp height 22.2m .871"
Total ht. 40.4mm 1.586"
Dome ht. 2.29mm .090"
Good deal.
Here is what I found on meteor 268 piston. I dont know which one though.
Meteor Piston Assembly 50mm for Husqvarna 266, 268 Jonsered 670 Chainsaws Replaces 501 65 88 03
Bore 49.96mm
Height 40.5mm
Head Type Flat
Piston Pin 12mm x 33mm x 8mm
Ring 50mm x 1.5mm (Caber F-Cast GH.F)
Compression/Pin Top to top of Piston 18mm
Compression/Pin Center to top of Piston 24mm
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Good info thk
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That is real good info, thanks.
There may be other pistons that would work better for increasing transfer flow, but this 268 sure was fast and easy to fit. The limiting factor on getting more performance from this saw, now seems to be the small intake tract. I did go back in to the jug and adjust some ports with that in mind, and here are the results:
https://www.youtube.com/watch?v=4X3ogrtSAUg&feature=youtube_gdata_player
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The saw overall cuts very good.
The engine seems to be leaning out as it gets some heat into it?
I would start out a little richer so when the heat built up, it was still rich enough?
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Yes, you'r right. The latest video was in "racing" tune, right on the ragged edge. No way would I take it to the woods like that, it has better low end with a working tune.
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Bigger the ports get, the lower the velocity. Be careful going to big, will make for poor low rpm power
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What air filter set up you have on that one? I wish mine had the mesh, but mine has the round $30 air filter like a HD.
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This saw also has the round, pleated paper style filter. I did try running it without the filter and cover, but it made very little difference. This saw has very good low end power with a good tune, so I don't think I made the upper transfers to big. It is however running best with almost 180° of intake duration, and quite a lot of blow down to keep the case compression up, and try to give the restriction in aspiration plenty of time to catch up. I think a much larger carb and intake would really help, with a little less intake duration. I will post all of the current timing numbers for discussion when I bring my book back to the house.
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Here are the current numbers for this job, this is where it will stay for now.
Squish: .021. comp:190psi. BD23° case compression:42°
Ex 102/156
In 96/168/84
Tr125/110
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So what do you think of how the echo saws exhaust exits are made? My 3120 hotsaw used the same idea.
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Kevin, Stepped port?
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Kevin, Stepped port?
Cant really remember that part off hand. But ends up O on exit.
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Ok I understand. ..
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Some McCullochs used an exhaust port design like that too. PM-800, PM600 series, etc...
Edit:
Nevermind. For some reason I thought you said "Q" instead of "O"...
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The "O" shaped ex does flow real well from entrance to exit, I just wish that there was more material on the sides at the entrance to allow more widening of the port. This one is wide enough for a work saw however. I also think that it could use a little more down angle.
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Reason I was asking I still think a 8000 would make a real good 5ci racesaw. Couple threads here on 8000 and 8000 on pipe.
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Could be, I sure would like to find a 8000/JD800 to try and liven up. The only one I ever ran was as lethargic as this 670, but did seem to have good torque at low speeds. I wouldn't be surprised if they used a full skirted, port windowed piston also.
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Could be, I sure would like to find a 8000/JD800 to try and liven up. The only one I ever ran was as lethargic as this 670, but did seem to have good torque at low speeds. I wouldn't be surprised if they used a full skirted, port windowed piston also.
The 800V I have has out cut bigger cc saws in hardwoods with 24" bars buried. 5200 85cc p60 98cc pic of OE and NE p+c 8000 http://chainsawrepair.createaforum.com/echo/echo-8000-piston-and-cylinder-pics-newest/msg5282/#msg5282
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That looks like it is just a larger version of the 670 engine, full skirted and windowed piston. Maybe one of the 8000's will show up here in the near future to get molested. If the 8000 has the same type of intake tract, with a larger bore, it's parts may be serviceable for an update to the 670.
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Did you ever try the different carbs for 6700 670 8000 on these? Testing with the bigger ones etc?
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No, I did not. The subject 670 in this thread went back to its owner with only the port work shown. I am interested in enough in making a good performer out of these saws, that I purchased a new cs680 to experiment with. It'll make a good winters project.
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No, I did not. The subject 670 in this thread went back to its owner with only the port work shown. I am interested in enough in making a good performer out of these saws, that I purchased a new cs680 to experiment with. It'll make a good winters project.
Carb info for 6700 670 680 8000 http://chainsawrepair.createaforum.com/echo/echo-carbs-6700-8000/
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Good info, thanks!