... its 1 of 2 things its either the cdi or its the magneto and the magneto rarely fails
That depends on the magneto, the new mags have no white wire and a better blue wire winding.
The Mags with a white wire have a coil tab soldered to the metal housing for engine ground, if you run these things too hot the weak solder can let the ground tab come free.
No ground to the spark plug, no spark.
Just Ohm for a dead short between the black wire and a head bolt.
If it's an open it's usually the ground tab.
One last critical thing...
Magnets can and do fail, just had to replace one in a new engine last month.
A weak magnet won't create enough current in the magneto to generate a big enough pulse for the CDI to create a spark.
One sure sign you have a weak magnet is when you replace the magneto.
If you can just hold it place with one hand and put all 4 bolts in it's weak, you have to fight that magneto around to get one bolt in, then fight to get another in if it's good.