Three-time Tour de France winner LeMond wants greater testing for motors by cycling officials.
"This is curable. This is fixable," LeMond said. "I don't trust it until they figure out ... how to take the motor out. I won't trust any victories of the Tour de France."
Varjas displayed his motorised bicycles in a Budapest bike shop, showing journalists how a secret switch can engage the motor or, in more sophisticated models, it engages as a rider's heart rate peaks.
One rider was caught with a secret motor last year and Jean Pierre Verdy, former French Anti-Doping Agency testing director, is concerned.
"It has been the last three to four years when I was told about the use of the motors," he said. "There's a problem. By 2015, everyone was complaining and I said, 'Something has got to be done.'"