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Left side crankcase breather (or lack of) is one way of determining if it is a late or early Super X engine. To the best of my knowledge this change came with the 1927 model. Although it is generally thought of as a 1928 change.
The following photos are of left side crankcases through the ages from 1925 to 1930. Unfortunately these are all loose cases and I don't have their matching timing side. Two of these cases are less than 70 units either side of Raposo's unit (SN 4159).
SN 1892, 1925 model with no crank case breather.
Drive Side SN1892.jpg
SN 4090, 1926 by Ballaks list but from my research it would seem to be an early 1927 model. It may well be that Ballaks do not distinguish model, just year. No crank case breather.
Drive Side SN4090.jpg
SN 4220, once again 1926 by Ballaks but my research leads to it being a 1927 model. Notice the drilled and tapped hole for a breather. Was the factory experimenting with additional/alternate breathers at this stage or was it a Service Bulletin to drill and tap for the breather? I dont know the real reason, all I can say is if you look at Raposo's engine which is only 61 units prior to this one, you can see the spot where the breather hole has been filled up.
Drive Side SN4220.jpg
SN A6974, 1930. Yes Ballaks says 1929 but Ive found too many 1930 spec bikes in the 6900 range to say thats true. Once again Model versus year of manufacture, could well have been made in 1929 for a 1930 year model. This one has the case boss for the breather.
Drive Side SN6974.jpg
From my photo archives I have SN 4953 which has the cast boss breather. I cant vouch for the originality of this engine in the chassis, but its fairly correct in all other areas for an early 1928 model.
4953 8.jpg
Summary on this, I personally believe that the engine in Raposo's frame is earlier than the frame and forks would suggest. I think an early 1929 should be somewhere in the mid 5000 serial range. Ill continue to check my archives for more solid information on this. The earliest 1929 Streamline serial I could find is on a very nice original bike SN A6032.
The following photos are of left side crankcases through the ages from 1925 to 1930. Unfortunately these are all loose cases and I don't have their matching timing side. Two of these cases are less than 70 units either side of Raposo's unit (SN 4159).
SN 1892, 1925 model with no crank case breather.
Drive Side SN1892.jpg
SN 4090, 1926 by Ballaks list but from my research it would seem to be an early 1927 model. It may well be that Ballaks do not distinguish model, just year. No crank case breather.
Drive Side SN4090.jpg
SN 4220, once again 1926 by Ballaks but my research leads to it being a 1927 model. Notice the drilled and tapped hole for a breather. Was the factory experimenting with additional/alternate breathers at this stage or was it a Service Bulletin to drill and tap for the breather? I dont know the real reason, all I can say is if you look at Raposo's engine which is only 61 units prior to this one, you can see the spot where the breather hole has been filled up.
Drive Side SN4220.jpg
SN A6974, 1930. Yes Ballaks says 1929 but Ive found too many 1930 spec bikes in the 6900 range to say thats true. Once again Model versus year of manufacture, could well have been made in 1929 for a 1930 year model. This one has the case boss for the breather.
Drive Side SN6974.jpg
From my photo archives I have SN 4953 which has the cast boss breather. I cant vouch for the originality of this engine in the chassis, but its fairly correct in all other areas for an early 1928 model.
4953 8.jpg
Summary on this, I personally believe that the engine in Raposo's frame is earlier than the frame and forks would suggest. I think an early 1929 should be somewhere in the mid 5000 serial range. Ill continue to check my archives for more solid information on this. The earliest 1929 Streamline serial I could find is on a very nice original bike SN A6032.
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