Well assuming that your dealers are competent carb rebuilders, i would have to move on to an intermittent ignition problem. Rings are either bad or their not, and your compression test tells me that they are ok. On the other hand if you have an intermittant ignition problem at certain RPM's or certain temperatures i dont care how hot of a plug you run, it will foul out if it doesnt get the electricity to spark. That is where i would turn. Either a CDI box goin bad, or possibly a coil, or the wires inbetween.
Polaris is my way out - Other people just use a door.
Polaris is my way out - Other people just use a door.