I have a roper 18t with an onan b48m. I recently put the brass floats in with the helper spring of course. It ran well for a few days after the install however now it keeps stalling. so I started at the basics and took the points cover off and found while I'm cranking I don't see a spark there, then it gets spark and fires up roght away. while its running it seems to loose spark again and stalls. It will crank for a while with no spark at the points before it seems to fire.
Could be a dirty, corroded, or even loose wire connection in the ignition system. That's where I would start. Coils and condensers and ignition switches can do strange things when going bad. Running a test lead from battery + to coil + may help narrow the problem down. Good spark would indicate a problem in the wiring before the coil, if the problem persists that would indicate coil, points or condenser is the problem.