There may be "no load" plugged in the outlet, but there is almost certainly a load someplace. The loss of engine speed and tripping breaker are very reliable indicators. Check the wiring between the breaker and receptacle(s), and the receptacle itself.

My 15-20 year old EX-1000 started acting up this year...it would die under load. In my case I pulled the carb off and cleaned the float & needle valve up...it works fine now. Fuel starvation due to a varnished-up carb.

Here is a link that might be useful: Honda EX-1000 Manual

From looking at the circuit diagram, my first suspicion is that you have an internal short in the outlet, either to ground or line to line. I would check this with a meter (with the machine not running).

Will do the required tests with a multimeter tonight. Still looking for the service/factory manual. ( do have an owners manual but its not so detailed). Thanks