Jamawani and others, thanks for the information! I'm definitely not a newbie to 'adventuring' but I have to say grizzly bears and heavy snowstorms are not something I had to worry about previously throughout my trips in Latin America & Mexico!

Motorcycling through cold weather is quite different to cycling, as you are not able to generate heat, but then are able to wear heavy suits and boots which would otherwise be restrictive for the cyclist. Freezing nights on the altiplano can be as cold as minus 20, or even down into the minus thirties or forties, but normally with zero humidity and always clear sunny skies the following day - being dry and cold is far preferable to wet and cold.

Jamawani, given your long experience of living out there in all seasons, would it be sensible then to pack for nightly lows of say 10/15c below zero, and daily riding conditions of anywhere from 25c above zero, to freezing? One thing which will be easier for me compared to touring in Mexico, etc, is having some of the best and well stocked outdoor stores in practically every medium sized town and the fantastic and reliable US postal service to bring me new equipment if not =)