Symptoms:

Crack the throttle real quick and the machine dies. Ease into throttle it runs fine.

At throttle, timing is retarded (If retarded is too far forward clockwise). Once machine hits a few thousand RPM's timing is dead nuts and remains up through the RPM range. Let off the throttle, timing goes back out and will die if throttle is pushed in quick.

Replaced:

Carb, ECM, CDI.

Have put four different CDI boxes on the machine. Two aftermarket that advance the timing (Machine won't even fire or idle in a bad way). Two OEM that retard it.

 

Have you removed the flywheel nut to see if the woodruff key has split and flywheel may have moved a little throwing off timing? Plus the problem could be carb related.Especially if it runs better at higher rpms. May be loading up with fuel at above an idle from a worn needle and seat.

 

That's next. Just trying to make sure I haven't missed anything obvious. Carb is new.