You might think that cutaway versions of motorcycle engines showing their inner workings are a recent phenomena but you would be very much mistaken as these have been around almost as long as the motorcycle itself.

Pre-war and post-war differences

Pre-war versions, such as this 1930s New Imperial Side Valve 500cc engine,

used angular or straight sectioning whilst later, post-war versions, such as this 1957 BSA A10 Road Rocket 650cc engine,

used curved as well as straight sections to show what’s going on inside.

Both of these pieces of motorcycle history were recently auctioned on 8 January 2015 in the Las Vegas Motorcycle Auction organised by Bonhams guided at US$5,000 to US$8,000 (£3,300 to £5,300) and US$15,000 to US$20,000 (£9,900 to £13,000) respectively.

The BSA Gold Star of the Earls Court Show

A number of other cutaway engines went under the hammer at this event but, to my mind for one, these were completely overshadowed by the Star of the 1956 Earl’s Court Show, a 1956 BSA B34 Gold Star Clubmans cutaway of a complete motorcycle mounted on a display stand with a fully motorized engine and suspension.

This incredible creation was first built for the 1953 Earl’s Court Show and featured a motorised drive train from the pistons driving the crankshaft through the clutch to the rear wheel. Motors built into the stand enabled both the wheels turn and the suspension to load and unload as if it were travelling along the road. The attention to detail is remarkable and the engineers clearly gave a lot of thought to every aspect. Even the damper bodies in the rear suspension were recreated in a clear acrylic so that the movement of the oil contained in them could be seen as the wheel went up and down. Three years later, for the 1956 show, the engineers brought it up to date from the original CB specification with the changes made to production machines to the DBD model as seen in these photographs.

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