Can anyone help me with my 1981 KX 125 electrical problem
 

Where to start ? bought this bike cheap previous owner said it needed a cdi So I bought the bike, ordered a cdi from ebay, the previous owner put in a aftermarket set of stator coils allready installed, So i got the cdi and guess what it ran, then I took it for a run and after heating up it died, So i investigated and found the spark looked weak, so I removed stator cover and gently mran some sandpaper over the rotor as i spun the engine over then sprayed with wd 40 now i have no spark, removed the aftermarket stator coil and put in the originals, still nothing So broke down and bought a new stator with coils, put it in the same No spark I only get 4.5 v out of the white wire with blue tracer nothing from the white with red, same with sloid blue and black???? question is could my rotor be bad??? how do you check it?????????