Junior Training.
 

Does anyone know how much a Junior (U23) Rider should train and how?. Also, does anyone know of any online guides for Junior training?.

Are you asking because you currently are without a coach, or do you simply want more explanation as far as what you should be doing?
Without any info on specializations, I'm going to say this straight; You should train enough to allow good grades in school, a rewarding social life, and a good nights sleep EVERY NIGHT. If any of those things gets messed up you should back off and back off quickly until you are a little more than fresh.