Author Topic: 3400 rings  (Read 185 times)

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Offline countryhog

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3400 rings
« on: April 14, 2015, 08:00:28 am »
got a 3400 torn down for cleaning. compression seemed a little low (no compression tester) so I measured squish (0.72) before taking cylinder off. got the following measurements:

 bore - 1.807"
 ring pin width - 0.055"
 measured gap (in cylinder) - 0.103"
 actual gap w/pin - 0.103 - 0.055 = 0.048"

 per Otto Gas Engine Works I should have a ring gap of 0.4% to 0.8% of the bore; 0.0072" to 0.0145"
 including pin width these translate to 0.0622" - 0.0695"

 should I spring for new rings or just use the old ones?
 i'm ditching the cylinder gasket to get smaller squish. will new rings make that big a difference?
now is never here but the past is always present.
semper fi ya'll

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Offline 660magnum

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Re: 3400 rings
« Reply #1 on: April 14, 2015, 12:19:58 pm »
While you have it down you should go ahead and replace the rings
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Offline Cut4fun

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Re: 3400 rings
« Reply #2 on: April 14, 2015, 01:01:18 pm »
If you do caber rings. I found Northwood Saw here in the states Clinton Corners, New York is much quicker then waiting on them from the Greek. 

http://northwoodsaw.com/store/index.php?l=product_list&c=78
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Offline Cut4fun

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Re: 3400 rings
« Reply #3 on: April 14, 2015, 01:08:16 pm »
Some info I have saved in the poulan 4000 thread.

4000 bore 49.2mm

3700 47.7mm

3400  46mm

The 3400 run around 125 to 135 psi.
The 3700 will run around 150 to 160 psi
The 4000 is the same as the 3700 they both have two thin rings and the only real difference is in
the bore size as far as compression goes.

I have seen the exception posted where someone got up to 175 psi on the 3700 and 4000 models.
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Offline countryhog

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Re: 3400 rings
« Reply #4 on: April 14, 2015, 03:08:06 pm »
Went ahead and ordered from northwoods
now is never here but the past is always present.
semper fi ya'll

Offline 3000 FPS

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Re: 3400 rings
« Reply #5 on: April 15, 2015, 07:50:40 pm »
It will not hurt to loose the base gasket but I usually have to take off another .020" to get a squish of around .025". 
I can then start to get 140 to 150 psi on the compression.  But these saws actually run very well and cut good at the stock compression and unless you just want to modify the saw I would not worry about it.

Rings are cheap and easy to do so I would replace them.
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Offline countryhog

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Re: 3400 rings
« Reply #6 on: April 27, 2015, 01:47:40 pm »
got the 46x1.5 rings from northwood. they were notched rings; had to file them down to get a fit. got it running and did a short cut but not enough to be conclusive. too busy
now is never here but the past is always present.
semper fi ya'll

Offline Cut4fun .

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Re: 3400 rings
« Reply #7 on: April 27, 2015, 02:03:05 pm »
I figured you would have to file them.   Did you file enough off  to not bind up in cylinder?

Is there any out there you dont have to file so you can install without work now days?
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Offline countryhog

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Re: 3400 rings
« Reply #8 on: April 28, 2015, 01:34:21 pm »
I never did remeasure it. duh? but have run it for short cuts couple times. last time ran for bout 5-10 minutes to get it good and warm. no issues yet. we'll see, eh?
now is never here but the past is always present.
semper fi ya'll

 

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