Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: jmester on January 15, 2013, 07:56:29 pm
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What are some of the gains and draw backs from advancing or retard the ignition timing? Also what is the purpose to do it.
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When advanced. You can gain some hp. But the saw may run hot and kick back when pull starting.
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Are the best gains on a ported saw or a stock saw? How will you know if you went to far advanced.
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It all depends on the saw also. The ms201T gets good gains. A ms660 gets good gains. I heard some saws it does nothing.... What others and myself are doing is shaving off half the fly wheel key and advancing it that much. As far as which gets the best gains(stock or ported) i cant answer that.
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How many degrees do you think that is with shaving half key down. Do you shave the whole key or just what sticks above the crankshaft. And yes the 201 does get some good gains. I did advance the timing on mine. Yes just trying to figure out what it made the engine do.
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By advancing the timing.
How many degrees do you think that is with shaving half key down. Do you shave the whole key or just what sticks above the crankshaft. And yes the 201 does get some good gains. I did advance the timing on mine. Yes just trying to figure out what it made the engine do.
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ABT half the key width is most do
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So you are saying half the entire key then.
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Take away half the width of the key in order to advance the flywheel that much.
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I see what you are saying. Does advancing the timing on a 361 give good gains.
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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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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 .
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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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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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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 .
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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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If your going that route. On the cheap and free http://forums.pelicanparts.com/uploads8/free_degree_wheel1153173072.jpg
Find you one and print it out https://www.google.com/search?q=degree+wheel&hl=en&client=firefox-a&hs=yN0&tbo=u&rls=org.mozilla:en-US:official&tbm=isch&source=univ&sa=X&ei=RYv4UIKXDeT02wWSm4GoDA&ved=0CFgQsAQ&biw=1366&bih=664
Doing what you are doing I wouldnt use one. I'm just a seat of the pants type though.
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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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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 .
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Thanks for the clarification. I get it now.
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Here's a link to the timing wheel I use. It is printed out on paper and glued to a piece of thin plywood but you could use aluminum or plastic.
http://www.rcuniverse.com/forum/fb.asp?m=11359655