china by train
 

Has anyone tried to put their bike on a train as freight through China to avoid guide fees? Would like to do this in Tibet through to Mongolia

I haven´t tried. But this could be very complicated... Do you mean like a train, that crosses into China from some neighbouring country? If not, then you would still have to get the bike across the border. And even if your bike was in a train, that crosses the border, is that a guarantee there won´t be any problems getting the bike into China?

There is a train from Mongolia through China. I thought that if we could travel on the train and had the bikes as freight we might avoid costly guide fees. we Would still have a carnet, but avoid the guide fees as much as possible.
i would like to travel from kathmandu into Tibet and then China mainland.

An interesting idea but I think the railway only goes as far as Lhasa and you need a guide and an organised tour in Tibet whether you are on your bike or not. You could look into flying the bike and perhaps yourselves over or take the shorter route from Kyrgyzstan to Pakistan which is a lot cheaper.