Author Topic: Tuning a saw  (Read 1336 times)

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Offline 05_sprcrw

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Tuning a saw
« on: April 06, 2011, 08:31:33 am »
I have a Husqvarna 394xp that I am going to tune properly (right now I just have it rich, it is always 4 stroking) I purchased my tach so I can set it by the numbers. I was wondering if it makes a difference on how fast the motor is turning with the size of the bar and chain on it.

For instance I cut with a 20" bar on the 394 90% of the time but will throw a 28" bar on from time to time. My initial thinking is that I would want to tune the saw with the smaller lighter chain on so that I don't over rev it by tuning the saw with a heavier chain on and then put the smaller lighter chain on. Is this true or will the engine run the same rpm with both chains (not under a load, so just for tuning purposes).

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Offline HolmenTree

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Re: Tuning a saw
« Reply #1 on: April 06, 2011, 09:23:34 am »
It won't make alot of difference from 20" to 28". But the powerband on the 394 will be a little different. At WOT rpm will be the same, but with the 20" b/c installed from idle to WOT the saw will respond quicker, being more "snappy".
Set your rpm at WOT for  what is called for.

Willard.
Making a living with a saw since age 16.

Offline 05_sprcrw

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Re: Tuning a saw
« Reply #2 on: April 06, 2011, 09:33:36 am »
Thanks I figured I was over thinking it but wanted to make sure. I figure I did everything else right on the rebuild (first one) and I didn't want to make some simple error and ruin it because I didn't ask.

Offline Cut4fun .

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Re: Tuning a saw
« Reply #3 on: April 06, 2011, 01:11:54 pm »
Here is Madsen's carb tuning with wave file to listen to.

http://www.madsens1.com/saw_carb_tune.htm
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Offline 05_sprcrw

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Re: Tuning a saw
« Reply #4 on: April 07, 2011, 08:41:15 am »
I have read the Madsens guide it definitely does a good job explaining how to tune a carb. I however don't trust my ears enough to do it this way. I have a tachometer coming to tune the saws to the rpms recommended by Husqvarna.   

Offline wannab12

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Re: Tuning a saw
« Reply #5 on: April 07, 2011, 08:55:22 am »
Is it a stock rebuild ? ported ? muff mod. only ? I think these will come into play as well. JMHO.

Steve

Offline mdavlee .

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Re: Tuning a saw
« Reply #6 on: April 07, 2011, 02:37:06 pm »
Try tuning the chainsaw by ear. Then put a tachometer on it to see where you are  by ear.

Offline 05_sprcrw

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Re: Tuning a saw
« Reply #7 on: April 07, 2011, 04:20:28 pm »
Is it a stock rebuild ? ported ? muff mod. only ? I think these will come into play as well. JMHO.

Steve

It is a stock rebuild. How do those come into play? Isn't the max rpms a saw can handle listed by the manufacturer so even if I modded it wouldn't I want to only tune it to factory specs. For this saw it is 12,500 rpms, if not then what can I safely go to with the saw, I plan on squishing the jug by taking out the gasket and using a gasket maker, and at most a muffler mod as well.

Offline man of stihl

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Re: Tuning a saw
« Reply #8 on: April 07, 2011, 05:36:55 pm »
Factory specs mean nothing to me. As long as it is 4 stroking out of the cut at WOT. you will be ok.
Ron

Offline Cut4fun .

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Re: Tuning a saw
« Reply #9 on: April 07, 2011, 06:19:01 pm »
Is it a stock rebuild ? ported ? muff mod. only ? I think these will come into play as well. JMHO.

Steve

It is a stock rebuild. How do those come into play? Isn't the max rpms a saw can handle listed by the manufacturer so even if I modded it wouldn't I want to only tune it to factory specs. For this saw it is 12,500 rpms, if not then what can I safely go to with the saw, I plan on squishing the jug by taking out the gasket and using a gasket maker, and at most a muffler mod as well.

Just say a stock 372xp is set at 13.5K max wot rpm. I have seen woods ported ones hitting 15K-17K out of the wood and the plugs look perfect. 
Now I would prefer to be on the rich side and clear up in the cut for cutting wood all day.
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