In December -06, I was with a group of 8, trying to enter Vietnam on 115cc scooters, with Thai plates, from Cambodia and Laos. Didn´t work. But maybe the size of our group also made it harder to succeed, we were pretty close many time (tried a total of 5 times on 4 different international border stations). It seems that they basically reject all foreign bikes, no matter if its 50 or 1500cc. I heard of someone, who made it with significant help from their embassy, but have no personal experience about that. The Vietnamese consulate in Phnom Penh certainly wasnt helpful at all.
I would imagine that crossing with your own vehicle from China to Vietnam could be even more complicated, as they´re less than friendly neighbours, and both have very strict customs regulations for vehicles, etc. But that´s just my assumption, could be wrong (and I think very few Westerners have tried crossing there, who knows if that´s actually good).
Maybe if you got time before you set off, trying to get some backup from your embassy could be worth trying. Very few authorities at the borders spoke any English (some spoke a little French, though!), so if you´re lucky enough to get some recommendation letter or anything on paper, make sure you´ll have it in Vietnamese, so they´ll be able to understand it.
Last edited by pecha72; 25 Feb 2009 at 19:31.