Yo Brooder mon,

When you say "bikeathon" do you mean by motorcycle or pedal bicycle? You probably aren't going to get anything in at the border of Nepal and Tibet. Scores of people have long dreamed to making it happen independently but none that I've heard of so far have done it.

Considering the sensitive nature of politics in China this year, it may be worth having a contingency plan other than the areas you are currently planning. Regarding importing your bike, It's also extremely unlikely unless you get it fixed by some folks in HongKong/GuangZhou. Otherwise, unless you're bringing it in for a special event, it's not likely to be imported legally but perhaps some others on here will have different opinions/ideas to offer.

CC