I need a lesson

[alderman]

I was reading that as a chainsaw accelerates the timing advances to get the spark out at the proper time. I think with modern electronics it probably is feasible but how did they do it in the old days? Any info would be appreciated as obviously I am a novice with much to learn.

 

[sedanman]

Points ignition was not capable of this, one reason that older saws don't rev like the new ones.

 

[Ancient One]

26 Degrees BTDC

Many of the older saws are set at 26 degrees before top dead center. You set this on the bench, as you gotta have the flywheel off to access the points. Playing with the points adjustment and in some cases shifting the coil laminations is it. I have a bunch of oldies, they generally peak at 5500 to 6000 RPM. One of the oldies is 7.5 cubic inches, you really have to let the saw know you are going to crank it up, otherwise it will yank your cranking hand back into the housing, ouch!

Modern electronic ignition modules are capable of advancing the spark for certain RPM's, retarding the spark for cranking (takes care of the Ouch! factor), and limiting the RPM to a maximum.

Now, we just need the electronic guys to start making ignition modules for the newer saws along the lines of Automobile performance chips. I can hear the claims now: 25 HP, 16,000 RPM, five cords to a tank!!!!!

 

[Crofter]

They do have the aftermarket electonic ignition modules you can install and eliminate the points. Some of them do have a variable ignition curve and a small number of revolutions before you get the first spark so you have time to build up flywheel momentum before it fires.

 

[Ancient One]

Electronic Module

Got one on a Mac 250, 4.9 cubic inch saw. No more points to change! Starts easier too. Now I am working with a newly manufactured coil (for a small motorcycle) that looks like it will fit the old Mac's. In search of the elusive hotter spark for the oldies.