the ignition (SSI i believe) crapped out a couple of years ago on my Crafstman Custom 10XL with 10 hp Tecumseh.
I had retrofitted the ignition with one off of a early 70s Chrysler, module, ballast, coil, etc...
I didnt have an appropriate pickup coil for the flywheel, so I improvised with help from online sources and made my own setup. it sucked. it idled great but would overdrive the module at high speed under load.
after being disgusted, I let it sit for a year and thought about what could be wrong.
I came to the conclusion that the pickup coil is the only thing it could be.
I didn't want to spend any money on this until I would be assured of success, so I made a different style of bracket, (adjustable) and used the abs front wheel speed sensor from a 98 to 2005 dodge 3/4 ton truck. its a two wire sensor, and the resistance is in the ballpark for a regular ignition pickup coil.
I got it running tonight with a few foul ups of my own making, and after fixing those, it runs AWESOME!
High speed, low speed, no load, full load, and anything I threw at it, it ran like a trooper, and never missed a beat. throttle response is great.
I don't have a camera or I would have gotten some pics, sorry (really, I mean it!)
Anyway, I just wanted to share what I found, and how I fixed it