I recently obtained an MSS Locomotive kit and these come with A4 exploded diagrams. I've scanned these diagrams, cleaned them up, and modified them for the different components and numbers used.

This file should be available for download in this posting. If not just send me a PM request for a copy.
If you are looking for the MSS Locomotive Assembly Instructions they are here - http://gardenrails.myfreeforum.org/sutra71145.php#71145
Chris Cairns.
(edited to include link to MSS Instructions).

Click to download file