Thanks everyone for your insight and suggestions. I finally tracked
the problem to a group of wires running along the top of my engine
block that was chaffing towards the rear of the engine and shorting
out the ignition. The wires had been wrapped in electrical tape and
the group of wires were zip-tied to a coolant hose running fore and
aft. When the throttle was moved full forward, linkage to the
carberator would press down on the hose and therefore press the wires
into the block and short out. I find it hard to believe someone from
the factory would attach these wires to a coolant hose...but there
they were. Thanks again for your help, Sean