These are links and things that may be useful in rebuilding a Honda CT125 (or any other single cylinder Honda that is around 30 years old).
The wiring diagram for an XL125 looks like this
Here is a copy of the users guide to the UK CT125. This also contains a wiring diagram and some basic maintenance notes.
There are exploded parts diagrams and all the part number for pretty much every component of the bike at this location.
If you need a physical copy of a manual, the best one that I’ve found so far is the Clymer Honda OHC 100-350cc 1969-82. Available from the Clymer website (The link is to the UK one, other countries have their own websites).
You can probably find a download of the Clymer manual here.
The remarkable Rhylan sent me a link to another list of Honda useful things to know when trying to order bits of any Honda.
For the many searches that reach here wondering how much fork oil to use. 130ml per fork will do you fine.
Emma has set up a Facebook site just for all those that love Honda CT125’s. You can find it here http://www.facebook.com/groups/HondaCT125