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Hi Dennis and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, other than the KILL switch, have you checked/bypassed the ignition switch? ...the ENGINE RUN/OFF switch? (depending on the version)
Still, it would appear to be either a fuel delivery issue (least likely) or an intermittent spark (most likely). Since "...CDI, battery, coil, spark plug and lead..." have all been replaced, then proposed preliminary tries (if have not been done):
Sorry Dennis but no. The pulser or pickup coil is co-located in the stator area. In old school this is the equivalent of a contact point or breaker. It triggers the ignition coil to fire or in this case, the CDI to discharge its capacitor to the ignition coil inducing the spark.
The stator area is at the left crankcase.
Please click HERE. Encircled in red is the pulser/pickup coil. The multiple coils are the stator windings.
Equally suspect would be the charging system. If the battery is getting too high a voltage, the ignition electronics kicks in auto-protect and shuts down the engine momentarily almost like a rev limiter.
This is simpler to test; run the GN125 with the voltage regulator temporarily disconnected and/or measure the battery voltage when revving.