Author Topic: timing  (Read 770 times)

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Offline 660magnum

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Re: timing
« Reply #10 on: January 16, 2013, 10:09:56 pm »
I have not done it on a 361.

From other engines I have done it makes them touchy to start.

The usual practice is to time some cuts - advance your flywheel a half key width and time some more cuts in the same wood and see if there was any improvement?

I suspect the 361 has advancing timing on the original coil and I would not recommend advancing the flywheel any more as it is already at 26 degrees while cutting and that is getting too close to all the advance you would want? At any rate, you will not be able to likely measure any improvement.
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Offline Al Smith

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Re: timing
« Reply #11 on: January 16, 2013, 11:27:39 pm »
As a normal rule some advance can be advantagious especially on a lower compression engine .The idea is to get maximum pressure at around top dead center .Some more modern saws of which I'm not certain of have autoadvancing ignition systems already .

It works very well on most McCullochs which have lower comp but I can't really say on a modern Stihl .

Offline jmester

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Re: timing
« Reply #12 on: January 17, 2013, 06:23:52 am »
Is there any way to tell by the coil that is on the saw, to tell if it is autoadvancing. I want to say the coil is very similar to the one on a 460.  Don't you lose some top end rpms by advancing the timing.
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Offline 660magnum

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Re: timing
« Reply #13 on: January 17, 2013, 10:00:10 am »
It's the other way around. They usually do better at high rpms - at least with the coils that were in the 036
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Offline Al Smith

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Re: timing
« Reply #14 on: January 17, 2013, 01:24:15 pm »
Most saws are timed at 26 to 28 advance .Some of the older lower compression at up to 35 which if that were done on a high comp saw all you'd get is a sore arm because you'd never get it started .

I've never done much on the Stihls but I have to some extent with  a few Macs .At about 30 advance is just about the limit of getting them started without pulling your arm out of the joint .

You could figure out by using the circumferance of the flywheel and checking by filing a little at  a time off the key how much you are advancing it .If it doesn't work put a new key back in the slot .

Offline jmester

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Re: timing
« Reply #15 on: January 17, 2013, 06:23:20 pm »
So you are saying use the flywheel as a degree wheel of sorts. If your wheel is 4 inches in circumference. Where would you say 30 degrees would be. Sorry if I am not getting it new to the whole timing thing.
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Offline Cut4fun

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Re: timing
« Reply #16 on: January 17, 2013, 06:39:53 pm »
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Offline jmester

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Re: timing
« Reply #17 on: January 17, 2013, 06:51:57 pm »
So if there is 64, 1/16 in four inches and you wanted to advance the timing to 30 degrees.  You would set it at 30/16. Correct? and that is from TDC at 0. I am trying to understand what al said.
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Offline Al Smith

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Re: timing
« Reply #18 on: January 17, 2013, 07:45:29 pm »
Not really .Circumferance of a circle is pi times diameter .So 3.1416 times 4 equals  15.57 rounded off .15.57 divided by 360 equals approx .043" .So every degree would move the mark 43 thou .So theoretically if you advanced it 1/8" or .125 it would be around 3 degrees give or take a tad .

A timing wheel is probabley easier and the larger it is the more accurate .This is not to say however you can use a 16" wheel on a chain saw .About 6 inchs would be about it .

The advance of course is from top dead center but if you were just shifting it you could lock the engine down anywhere in the rotation .

Now if you are advancing the timing using the key you have to move it in direction of rotation .Using a slotted coil the opposite .

Offline jmester

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Re: timing
« Reply #19 on: January 17, 2013, 07:49:31 pm »
Thanks for the clarification. I get it now.
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