For 1927 the 3.46hp Royal Enfield came in 2 models. The Model 350, a side valve of 346 cc, and the Model 351, a OHV of the same capacity. The 346 cc model was first introduced in 1924 and came fitted with Royal Enfields commonly used all chain drive 2 speed countershaft. Upgrades for 1925 saw the introduction of the well known Sturmey Archer 3 speed gearbox and the first year for the internal expanding drum front brake. There were small changes but in the main this model remained the same from 1925 until 1928 when the new frame was introduced incorporating the more modern design of saddle type petrol tanks.
The parts manual is interesting as it also lists the parts for the lightweight sidecar chassis. Lightweight it would had to have been, as a solo machine the speed was around 35 mph. With a unladen sidecar attached it would have been considerably slower. But then the roads were slower as well.
Click on the front cover below to see the complete manual.
It is a 6.6M PDF so you will need Adobe Acrobat Reader to view it.