BMW Motorrad Spezial

Sunbeam S7

Sunbeam S7 motorcycle
By guest writer Diesel of Visual Gratification. Erling Poppe designed the beautiful Sunbeam S7 based on the BMW R75 of the late 40s. While the R75 had a horizontally-opposed boxer twin, the S7 engine was an inline 500cc twin shaft-driven to the rear wheel. It was a technology marvel with an overhead-camshaft engine, shaft drive and plunger rear suspension—making it too expensive for many buyers. Wisely, the later S7 Deluxe and S8 came with fewer technologies and sold better. Built in Redditch, England, the S7 was dubbed the ‘Tourer’ and a little more than 200 were built. The S7 Deluxe fared better—selling double figures over its predecessor. (It was the S8, a ‘Sports’ model with increased performance from higher compression pistons, that was the sales success of the trio.) The S7 came in two colours, black and mist green, but its ‘balloon’ tyres were a suspect at high speeds. However, for obvious reasons, it’s one of the most sought-after machines today. The photo here is from the collection of CMM (Collezione Motociclistica Milanese), a museum in Milan—and the image shows one of the very last production S7 bikes. [Photographer and image copyright Giovanni Cabassi.]

  • The Phantom

    Lovely bike. Probably the first older bike that I ever got excited about – I know where there is an unrestored one…

  • Andrew Webster

    In the late 60s I actually owned one of these, hitched up to a Double Adult sidecar (probably a mistake, as it was slow enough as a solo). I paid £10 for it, and sold it for the same amount a year later. Beautifully made, but so many design flaws. Mine had passed through many hands and home mechanics and that didn’t add to its charms. The sump had several spoanners in it from the previous forgetfull owner and thoroughly incompetent mechanic. I couldn’t wait to get rid of it. I got a Triumph T110 which was a superior bike in nearly all respects. Twice as fast, far more reliable, far better handling. There’s a reason some of these old bikes are so collectible now – nobody with any sense bought them new. Many of the collectible vehicles today were the lemons of yesterday. EG the Sunbeam S7 had an alternator on the main shaft, so that when the main bearing was even a little bit worn, it chewed up the commutator. Mine used to set on fire regularly, as the p***pot Amal carb was nicely placed in between the exhaust outlets, heating up the fuel to incendiary point when you were stationary. I still have the scars on my arm from one such incident. I wish I had kept the Sunbeam though for obvious reasons.

  • Fred Bloggs

    I came across one of these a few weeks ago and chatted to the guy who was restoring it. His views were remarkably similar to Andrew Websters. This is a beautiful bike to look at, but pretty useless for anything else. Slow, underpowered, unreliable and pretty evil to ride! Perfect bike for the collector.

  • kim scholer

    Oddly, in the mid-50s a Japanese version was made too; It had a 250 cc ohc engine, a rear swingarm (incorporeting a more conventional BMW style rear drive) and an Earles type front fork. Power output was 11-13.5 hp.

  • I like the old leaky Sunbeam…the manual siad something like …before you join your friends give the shaft drive a wipe with a rag…interesting.

  • What sould I say? Perfect bike, perfect picture … I fell in love
    I was enthusiastic since I’ve seen the pic of a Sunbeam S7 more than ten years ago.

  • Andrew Webster

    Another thing I remember about my Sunbeam was that you had to adjust the rubber “snubbers” that acted as an engine steady and balance against torque reaction. Unless you got them dead right, the whole bike vibrated in a horrible fashion. Once adjusted correctly, the engine was one of the smoothest i have ever experienced. Low power equalled tractability and smoothness. The lower powered Triumphs were the same – 3TAs, 5TAs, T100As etc. I think twins of this era lose their smoothness with higher outputs. Norton solved that by isolating the engine from the frame, and the Sunbeam had a similar ingenious scheme some 15 years earlier.

  • kim scholer

    BMW R27 (1960-66) and Swiss military Condors with Ducati engines (1960s through 70s) used rubber mounting too. Anyone else out there know something?

  • Andrew Webster

    And of course, another vibration monster, the Harley Davidson Sportster introduced the “revolutionary” idea of rubber mounting the engine about five years ago. I’ve no idea how it worked, but my friend had an earlier model which vibrated so insanely that everything had to be wired and loctited on.

  • kim scholer

    The system the newer Harleys use is much like the Norton Isolastic system. A bit improved, of course, but with the engine/driveline isolated from the frame and front end.

  • Eric Lenson

    I had a S8 Deluxe in the late sixties, used to ride it to the where I did my apprenticeship at Henly Beach in South Austarlia. Yes I agree with some previous comments about reliability especially the ignition, and the generator, but I could always get it going regardless. Rode it in all conditions for three years until I could afford a 700 Royal Enfield. The Enfield made the poor old Sunbeam seem like it had come out of the Ark. Yet after all these years the Sunbeam still has a charm that no other bike I have ridden has, wish I still had it.

  • Eric Lenson

    Correction to my previous posting………it was a S7 Deluxe 1956 vintage. The S8 was the same thing really but did not look as nice as the fat tyred S7.

  • Mattro

    that brake lever is interesting — inverted fulcrum and in-bar wiring? i’m SO stealing that!