Chain saw has no spark

I have a McCulloch Pro Mac 605 20-inch chainsaw that has been starting and performing well with recent heavy use until a few days ago. Now it has lost its spark. I have (1) replaced plug, (2) blown and wiped all dust and debris from around coil, (3) set correct gap, (4) disconnected kill-switch wire at the coil terminal, (5) examined plug wire and it looks clean, (6) tested for spark by removing and grounding plug, hooking up a B&S spark tester, even holding onto the plug as I cranked the engine (Yikes!) -- result is no hint of a spark. I don't know how to test a small-engine ignition coil other than what I've already tried, but before I conclude I have a bad coil, I'm soliciting your opinions --would you guess probably the coil or maybe something else I've overlooked? With a new coil running around $65, I hate to make a mistake. I know that cost is high for an old McCulloch, but it's a great saw when it is working (one of the few McCullochs that get generally good comments from users). All advice is appreciated. (FWIW, I don't want or need to buy a new saw; I already have two other 20-inch saws and half a dozen smaller ones. I'd just like to fix the Pro Mac rather than throw it away.)
 
Hello rossow (MN),

You can trace the grounding wire to the switch,
If it is pinched or touching metal it would kill the spark! otherwise, bite the bullet and get the coil. I too have some McCulloch saws. Like them all. Here is a picture of my work horse,
Pro Mac 610 vintage 1981!
a160039.jpg
 
Pull the flywheel and examine the key. It is not uncommon for the key to shear or partially shear mistiming the magneto.

Dean
 
I have fixed a boat load of these 600 series Mac saws. Check the key but I have also seen the metal hub that is cast into the flywheel TURN! The only way to test these is on the saw. Take the plug out so you can spin it realy good. DON"T break your recoil!!!If you get spark with a FAST spin but not a slow normal start the saw spin then the module is bad and the auto spark advance is dead. I have one 605, about twelve 610 saws, and 10 650 saws. That is just the 600 series! I would go for the coil. If you like flea markets these saws show up now and then and I have purchased a bunch for parts. Most have carb or broken parts trouble. Coils are not realy coils but a module. They do go bad but not that often. Let us know. Jeffcat
 
Try this--
Remove sparkplug
Put few drops of two cycle into the cylinder
Remove flywheel cover
With a variable speed drill, use the proper size socket and spin the flywheel counter clockwise. Start slow and gradually increase speed. Do this while observing spark, and after a few seconds remove the drill/socket while running. In SOME cases, this will revive coil, especially one without use in some time.
I have revived some coils and others were toast.
Also, be aware that you will be Loosening flywheel nut and that is the reason for starting slow and removing socket under power. Work carefully--don't want the flywheel to come off.
This cost nothing and might work.
 
Boy, that is a new one. Never heard of reviving a coil. I think the points started making contact after turning it over for a while
 

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