What factor might have slowed the adoption speed of the earliest, heaviest motorized conversions?

Answer

The average strong cyclist might have been just as fast or faster.

One overlooked factor contributing to the slow mass adoption of the first gasoline-powered motorized bicycle conversions was their comparatively poor performance metrics relative to human power. These early machines were often heavy due to engine size, utilized inefficient engines, and placed considerable stress on bicycle frames not designed for the vibration and weight. Consequently, an average, fit cyclist operating a well-maintained, purely pedal-powered bicycle could frequently match or even surpass the speed and reliability offered by these initial, cumbersome motorized contraptions, thereby reducing the immediate incentive for widespread consumer purchase.

What factor might have slowed the adoption speed of the earliest, heaviest motorized conversions?
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