Fuel problem

[bocar640]

I have a 1999 60 HP two stroke that appears to run on two cylinders at approximately 1200 revs and then clears and runs beautifully at all other revs I stripped the carbies down, no dirt anywhere but still the same. The unit is perfect otherwise. I have owned it for 11 years and have done a fair bit with it. If there is any solution out there I would appreciate the help. I have a screw on fuel filter as well as the one on the engine
Regards

[rodbolt17]

test the CDI output at the problem RPM.
that will narrow it down to fuel or spark.