Author Topic: Tuning carb with a tach?  (Read 175 times)

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Offline eriksat1

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Tuning carb with a tach?
« on: February 28, 2014, 12:30:31 pm »
I wasn't sure where to post this? I am having a hard time getting a straight answer. It is not a Husqvarna only question. I read and watched video's and know everything there is about tuning "by ear", tuning in the wood etc. Now what if you are in a shop with a good tach trying to tune a saw with no wood available to cut into, or say a guy is totally deaf and can not hear the 4 stroking. Is there no way to correctly tune the high speed with a tach only? I can't get a straight answer.

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Offline 660magnum

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Re: Tuning carb with a tach?
« Reply #1 on: February 28, 2014, 12:44:16 pm »
If the practical time honored "in-the-wood" technique is not available or there or other impairments to an individuals senses, then there is not anything wrong with tach tuning as long as you know the point to tune it to. 
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Offline Cut4fun .

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Re: Tuning carb with a tach?
« Reply #2 on: February 28, 2014, 02:15:13 pm »
If it were me and was tuning with a tach and couldnt hear.  I would find my model of chainsaw look up max wot rpm. Say it is 13,500. I then would set my carb to 12-12.5K on tach. I rather be little rich then lean side. JMO
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Offline eriksat1

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Re: Tuning carb with a tach?
« Reply #3 on: February 28, 2014, 02:16:30 pm »
So what is the proper procedure? Say the book spec says high rpm 13,500 on a 372xp. And it has a rev limiting coil.
So go way rich with the high screw then lean back to 13,500 like the book spec says, then richen back up again to 12,500? Why does the book say 13,500 then? I doubt they want you to over rev. but that is the spec.

Offline 660magnum

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Re: Tuning carb with a tach?
« Reply #4 on: February 28, 2014, 02:25:10 pm »
You will need to tune it a little less than that. You will find that you will need to tune that saw to 13,000 even for it to sound correctly to you in the wood.

Take note that you should re-tune the saw every time you go to use it and the temperature is significantly different.

Also a saw in a big cut will run leaner after it gets hot than it did in the beginning. So If you are going to do some big wood for the size of the chainsaw, you need to begin a little richer.

Also you can burn up a saw in big wood even with it on the rich side if the chain is too aggressive or big and you push too hard
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Offline eriksat1

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Re: Tuning carb with a tach?
« Reply #5 on: February 28, 2014, 02:35:16 pm »
Since I bought a good tach I have no problem checking it every time I cut. This winter has been crazy cold. But one day it might be +25f the next day minus -10f.
So go way rich then lean out cw 1/8 turn at a time until rpm rises back up to 13,500 then richen back up ccw till it drops to about 13,000 sound about right??

Offline 660magnum

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Re: Tuning carb with a tach?
« Reply #6 on: February 28, 2014, 02:37:45 pm »
That sounds about right
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Offline eriksat1

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Re: Tuning carb with a tach?
« Reply #7 on: February 28, 2014, 02:45:41 pm »
Thanks,
For something that simple it was hard to get anyone to commit to an answer. My Husky dealer told me with a rev limiting coil the only way you could set it correctly was with a tach, but he wasn't willing to tell me exactly how to do it he wanted me to bring it to him. How can I do that every time the temperature swings 30 or 40 degrees in a day. So I bought a tach.

Offline 660magnum

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Re: Tuning carb with a tach?
« Reply #8 on: February 28, 2014, 02:57:25 pm »
I don't like the rev limiters.

Other than replacing the coil with a non limited one, you have to keep the saw rich enough that you know that it is not into the rev limiter. Then lean it out enough to clean up in the wood you are cutting.
 
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Offline eriksat1

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Re: Tuning carb with a tach?
« Reply #9 on: February 28, 2014, 03:05:23 pm »
I was having a hard time telling the difference between 4 stroking and hitting the rev limiter.

 

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