Ignition Timing

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trappermike

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Ah yes,who among us hasn't advanced the timing a little,slotting the module mounts or using a modified key? Fine for work saw mods but when we want more power and get technical we gotta know what we are doing.
My first question to you is-how many degrees BTDC is your stock or modified engine firing at? Most people have no idea. That's fine for simple mods,but when you get more serious you NEED to know where your ignition is firing BTDC,and where it is when you alter it. Over advanced ignition timing will burn a motor up pretty fast.
So go find TDC on your motor and mark it on the case and flywheel as accurate as you can. I like to use some model paint and a tiny brush to make marks that really stand out under a timing strobe light. Then back up your motor to 25 degrees BTDC,make a mark,then back up and make a mark at 30 degrees BTDC.
Now pull the spark plug and spin the motor with a drill with the timing light connected,and see exactly where it is. I prefer low-light in the shop during these tests. So it will show exactly what the stock timing is,and where it is when you make mods.
Generally the hotter the motor is(race) the less advance it will like before cooking the piston. Old stock motors can survive more advance than newer hotter ones.
For you guys just playing with timing on work modded saws,you can get away with a lot sometimes,but for someone building a serious motor,we cannot guess where the timing is or care...
Some of the really old saws had timing of like 35 degrees BTDC,(a lot!)which would cook a normal saw fast,but they were burning a slurry of 16-1 mix,using #40 motor oil,this fuel was so thick with oil it burned very slow,with a modern 50-1 mix,these motors will die,which is why I encourage anyone with an antique saw running on modern fuel to retard ignition timing.
So do your homework,find out what your stock timing is and then see the changes you make. Be professional.
 
TM, thanks for the write up. Now I am currently trying to get another timing light since someone was kind enough to break into my storage and make off with over 5K worth of my tools and other things. Anyway I haven't been playing with the timing on saws yet and I am getting ready to start, what little I have seen on this (and there isn't a whole lot out there that I have found) is 28 degrees is about the most you want to push a work saw and I noticed you said 25-30 degrees, is this about what you are saying as well with a 40:1/50:1 mix in a modern saw?
 
TM, thanks for the write up. Now I am currently trying to get another timing light since someone was kind enough to break into my storage and make off with over 5K worth of my tools and other things. Anyway I haven't been playing with the timing on saws yet and I am getting ready to start, what little I have seen on this (and there isn't a whole lot out there that I have found) is 28 degrees is about the most you want to push a work saw and I noticed you said 25-30 degrees, is this about what you are saying as well with a 40:1/50:1 mix in a modern saw?
What type of timing light do you need? Just a regular, clip on to a car battery one?
 
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