Zac,
As you will also have now discovered, the mag is gear driven.
As far as I know, there was no handbook produced for the DT models, just a spares list (unillustrated) for the K29 (1929) DT model. There was also a data sheet the factory provided to riders with various settings and jettings. However do not get too excited because it was for machines set up to run 50-50 petrol-benzol on the cinders. The later was posted here on the forum years ago. Should not be too hard to find doing a search.
-Doug