Mystery Norton

Rob recently bought yet another pile of bits that will one day make a Norton; he had a few already but this one appeared to be so special that he could not let it go. The Norton is an OHC model using a Carroll engine. The engine and frame numbers (respectively CS49056 and 42864) match and identify the bike as a 1931 CS1 that was despatched on the 13th of October 1930 to the famous Liverpool dealer and tuner Victor Horsman. The bike uses the Enfield rear hub but in combination with a two stay frame. 1931 CS1 Nortons typically use the Enfield rear hub but in combination with a three stay frame. (Though the 350cc CJ models did already use a two stay frame in combination with the Enfield hub in those years.) 

The engine has a few remarkable features; it is an early engine, as identified by the absence of the oilfilterbolt in the crankcase timing case. Further, the cambox has a provision to drain excess oil via an external oil line fitted to the right side of the cambox. There are adjusters for the felts that seal the rockers on top of the cambox; not only at the bottom as on later models. The engine uses coil valve springs and the inspection cover looks different. The exhaust pipe still sits at the left side of the engine. In that light have a look at the text below that I copied from Paul Norman's website: 

"The new model was offered to the public late in 1930 (although still being advertised as the earlier CS1 and CJ model types) and also boasted a modified and updated chassis. The earliest of the Carroll engines had a slightly different cylinder stud spacing to later engines, and did not have an oil pressure indicator or oil filter in the crankcase timing case. Also apparent in the earliest photos of the racing model in 1930 was an additional oil pipe running from the right side of the front cambox, down to the corresponding area of the timing case. I assume this was to assist oil drainage, although it was removed by the time the 1931 model range was introduced. This earliest of models also looked to have a top bevel inspection cover with a slightly different curve to later models. Another interesting point with the early versions of the engine is that they were fitted with standard coil valve springs. This is surprising really, when one of the International and Manx engines most well known and refining features was its later use of exposed hairpin valve springs, with associated oil loss! Hairpin springs were not introduced until 1934."

Hurried drawings made for the 1929 Olympia show are probably not correct but some features, like the oil return line from the cambox are clearly visible. It's tempting to speculate that Rob has one of these rare and early models as described by Paul. Does anyone recognize this Norton?