Here's the answer I gave to a similar question back in January. It was in response to someone who was planning a trip and wanted to learn some skills before they left. Hope it helps:

A couple of years ago I retired from a life time of earning a crust firstly by repairing motorcycles and then the last 22 years by teaching in a FE college engineering department. One of my responsibilities there was to set up a motorcycle repair and maintenance course for students intending to go on to find apprenticeships. So I write with some experience.
First, I would think about the time left before you depart on your intended trip and consider what you skills can realistically manage to master. It takes a long time for a novice to learn the underpinning knowledge and master the skills necessary to become competent. So unless you are looking at taking your trip some years in the future, I would say it would probably be better just to learn some essential skills before you go. For example tyre changing (there is a good HORIZONS video that deals with this), puncture repair, how to adjust and replace a drive chain, how to replace brake shoes and / or pads and other simple maintenance and repairs.
Get hold of either a Haynes or Clymer manual for your bike and have a go. Use the manual and start with the simple stuff. Chain adjustment, topping up fluids, replacing bulbs etc and build your confidence. Then move on to practicing removing the wheels, start with the front since it is usually easier. Then you can progress to other more difficult tasks. It's all PRACTICE, PRACTICE, as far as dismantling, reassembly and maintenance is concerned.
Where the real skill comes in is being able to make a diagnosis and that will come from understanding how the various systems work and the experience you have already gleaned. To help you understand how systems work you could look at the various tech books published by Haynes and a book published by Pearson called Motorcycle Maintenance and Repair, which is for work based learning courses but it will give a useful insight into understanding motorcycles.
Above all don't be afraid to have a go. You will inevitably make mistakes, but a few mistake made before you go should result in less on the road.

Two good books for amateur motorcycle repairers are:

Motorcycle Workshop Practice Techbook

Motorcycle Electrical Techbook

Another good place I have heard of if you are in or near London, is the Oval Motorcycle Centre. Oval Motorcycle Centre Motorcycle DIY workshop, maintenance, service, repair and training workshop
Here they rent out space and tools to diy repairers and also have experienced staff on hand to offer help and advice.

Or you could try checking FE colleges in your area, sometimes they run evening courses for diy motor and/or motorcycle mechanics.