Start at the coil [Ohms ] then connections ,,then points &condencer, . the soarse coil needs checked ,[ ohms] , Or,,,,you can fit CDI, Lots of systems out there nowadays,
i did fir DT400 cdi system on my 250. the flywheels are different ,so need the 400 flywheel . its same fit , just has 4 magnets, for pick-up timing,