Why are there no black or asian riders on the Tour de France?

I think that the reason track cycling is big in Japan is because of the parallels with zen / discipline, that make the sport socially respectable.

The reason why Kierin became big in Japan was during the war the Japaneses ate most of the horses/dogs, and with the population growth there was very little suitable land to keep horses. So after the war they started to gamble on Keirin racing. At some of the bigger events more money is gambled on one night than the four days of the Grand National meeting.