Why can't the tricycle shift gears?

[SanSienna]

It may be due to slippage in the hydraulic-operated clutch. Below is relevant information about vehicle gear shifting: Precautions: When downshifting, use the method of double-clutching with a blip of the throttle. The principle of downshifting with a throttle blip is: the faster the speed, the larger the "throttle blip"; the slower the speed, the smaller the "throttle blip"; at low engine speeds, the "throttle blip" should be larger; at high engine speeds, the "throttle blip" should be smaller; on flat roads, the "throttle blip" should be larger; when going uphill, the "throttle blip" should be smaller. Techniques: Gear shifting should be timely, accurate, smooth, and swift. When starting the vehicle, generally use the low gear (first gear). After starting, as long as road conditions permit, quickly and promptly shift up to higher gears.