I have a weed-eater engine, brand unknown, that will not spark. I attached it to a test stand and tried to start it up and there is no spark from the magneto. I tried a magneto from an operational engine and still no spark. What is it that I am doing wrong?

Did you check the plug and/or the ignition wiring?
Oh,by the way ,in some weedeaters like the poulan 21 I have (model GTI 15 T),if you run them on nitro based glow fuel,at the higher rpms ,you can shut the ignition off and they will still run!
And this is with no adjustment to the engine.And it runs smoothly too!

how bout your coil to flywheel gap? good rule of thum is no more than a business cards thickness. also without knowing the manufacture you might have an engine that also requires an electronic ignition module. I have one of those that came from a trimmer line called Tanaka,I think thats the right spelling. put a couple of good photos up here so we can help figure out what you have first. Piper