Road Test: 1925 Sunbeam 'Crocodile'

The Vintagent Road Tests come straight from the saddle of the world’s rarest motorcycles.  Catch the Road Test series here.

It takes quite a draw to lure me onto an airplane and cross the Atlantic for a ride on a motorcycle lasting only a few miles.  But, oh what a motorcycle, and oh what a ride, were dangled before me last Spring, and it all suddenly made sense: yes, I’ll make the trip to the second running of the Auerberg Klassik hillclimb.  The motorcycle in question is an ex-factory racing Sunbeam, one of 5 built in 1925, Sunbeam’s heyday, with an experimental overhead-camshaft valve operation.  Four machines and one loose engine remain, which is remarkable given the bike was only used for one year, and not further developed by Sunbeam, who missed the boat to the Future by sticking to what it knew best: pushrod OHV single-cylinder motorcycles.

The experimental OHC Sunbeam was given the memorable title of ‘Crocodile’ by factory staff, supposedly because it went ‘tick tock’ like the crocodile in ‘Peter Pan’.  That croc had swallowed a clock, and unnerved Captain Hook whenever he could hear it ticking.  Having ridden its namesake, I can’t understand where the reputation for noise arose, as the Sunbeam’s cam drive neither ticks nor tocks nor even rattles: it is as all Sunbeams are, mechanically quiet and civilized.  Well, slightly less civilized than my 1928 Model TT90, but that’s another story: the path Sunbeam took instead of developing the Crocodile.  The Model 90 is genteel in its approach, and can be left in third gear most of the time, relying on its heavy flywheels to hurtle its slight 250lb mass from a jogging pace to a terrifying actual 90mph-ish.  The Crocodile, by contrast, felt like a real Grand Prix machine, and responded best to a wide open throttle to wind the engine out in the gears: to paraphrase TE Lawrence, it’s ‘a slightly skittish creature, with a touch of blood in it.’

Despite the difference in its valve operation from every other pre-War Sunbeam, the Crocodile is remarkably orthodox.  Everything but the motor is identical to the overhead-valve Model 9 of 1925, and even that is familiar.  The Crocodile shares its cylinder barrel and head with the pushrod job (the dual pushrod cutaways in the cast-iron barrel and head are still there) with suitable modifications for a tower shaft cam drive, and a cambox bolted atop the iron cylinder head. As well, a wet sump was welded onto the crankcases, which is unusual, because the crankcases are unique to the Crocodile, or at least the timing side is, of necessity.  Whether the sump was an afterthought or it was simply expedient to gas-weld an extension, I don’t know, but it does hold oil, which is circulated with the usual Sunbeam mechanical oil pump.  Doubly unusual for a dry-sump motor is a typical Sunbeam oil tank bolted to the saddle tube!  Apparently the external tank was only used in long-distance events like the Isle of Man TT, when more oil for the total-loss lubrication system was needed to finish a race.

There wasn’t much lacking in 1925 with the Sunbeam chassis, as compared with every other make available, and Sunbeam relied on light weight, good balance, and a moderate steering head angle for excellent handling.  There’s very little in the way of suspension, with the back end rigid, and the Druid side-spring front forks boasting perhaps 2″ of travel, with André friction dampers attached to moderates even that limited movement.  Thus, with beaded-edge tires inflated to 40lbs, one feels every pebble in the road, and the extra light weight of the whole machine means it’s easy to get the whole plot airborne over bumps…but it’s also easy to keep the thing in line, as it weighs nothing.  Thus it would be wisest to pick smooth roads for a road test, or any other hot ride, but my Crocodile’s test track had plenty of bumps and corners, giving a full feedback on how the animal tracks over undulations and corners, and combinations of both.

My test ride was taken over a timed series of sprints just outside the village of Bernbueren, deep in Bavaria, for the second running of the Auerberg Klassik hillclimb.  As the hillclimb track was lined with a mere 10,000 people watching, cheering, and wanting entertainment, one might say this road test was conducted under unusual circumstances, and just a little pressure.  It’s fair to say I was determined that the crowd’s entertainments would not include watching a priceless factory racer skittering sideways across the blacktop.  A few facts conspired against me: the Crocodile has, typical with most 1920s machines, very poor brakes, but also possesses stirring acceleration and a top speed in the 90mph range.  And, as it handles beautifully, as Sunbeams do, I found it joyful to move swiftly under full throttle, and had to keep reminding myself the gorgeous creature between my legs was not mine.

The Auerberg course proved a perfect test track, in a way, being fairly steep, and very winding, with straight stretches on which to build speed.  A light motorcycle has advantages on such a course, and I was on a greyhound of a racer.  Which, as it proved, bore racing #1 for being the oldest machine of 200+ racing motorcycles competing over 3 timed runs on the weekend.  Thus I rode the Crocodile both first and last: first up the hill, last down, and downhill proved more worrying than the fast bits: there were moments when I Fred Flinstone’d the tarmac to avoid other riders, who had the audacity to stop mid-course for an orderly lineup back to the starting gate: how perfectly Germanic, but not much fun for a man with no brakes.  Oh yes, that happened too: on the second downhill run, the antediluvian rear brake material simply gave up, and began flaking off in smoky bits!  Yabba dabba doo!

But that wasn’t a problem going uphill, because brakes only slow you down. Keeping up momentum around corners is the key to riding an old motorcycle quickly, so apex braking was out of the question anyway: I simply eased off the twistgrip throttle (a very early one at that, although I’m not sure if it’s an original piece – my TT90 has a lever throttle, which is typical pre-1930).  The short wheelbase and easy handling meant course corrections mid-corner were easy, and the throttle could be applied as early as one dared towards the corner exit.

The Crocodile, like my TT90, is remarkably easy to start: tickle the carb, knock the ignition timing lever back 1/8″, push the tank-side gear lever into first, roll the whole machine back onto the compression stroke, squeeze the clutch lever, then paddle (in the saddle) forward three paces, drop the clutch, and voila, 9 times out of 10 you’re bonking away merrily.  No run-and-bump is necessary, as the compression isn’t high, and the flywheels heavy enough to keep momentum going over the second and third compression cycles, to ensure an easy start.  On a road run, I would simply have driven off gently after that, to warm up the engine for a mile or three, before winding up the revs to explore speed, but there was to be no touring on my test ride. I rhythmically revved the engine to warm it up, treating the other riders behind me, and the crowd, to a glorious bark from the Crocodile’s twin exhaust pipes.  (As one can see in the video above)

On being flagged off, the throttle was twisted all the way back, and I let the engine run through first gear, which on a 3-speed ‘box is a surprisingly long time: the ratios are very close, and unlike a 4-speed, one actually uses first in a race in slow corners – it’s very high-geared.  The engine is remarkably smooth throughout the rev range, and despite the ultralight chassis, there’s no harmonic vibration through footrests, saddle, or ‘bars.  Yes I could feel the engine, but somehow the Sunbeam engineers knew how to keep spinning iron smooth.  I doubt I exceeded 5500rpm, while 6200rpm is the typical redline for a crowded-roller big end bearing, and I wan’t going to lurk in that rev region anyway.

Within 200 yards it was time to shift into middle gear, which was easy as the clutch worked cleanly, and the shift gate is positive in locating the long lever securely.  That soon brought me to the first left-hand curve, followed by some left-rights as the road changed from field to trees, before straightening out for a steeper open uphill section of perhaps 1/2 mile, where it was possible to shift into third gear briefly.  It was hardly worth the effort, though, as another series of bends of increasing complexity loomed, and second was the cog of choice almost the whole way up.  I say almost, because just near the top, after emerging from a tunnel of forest, was a sharp right-hand turn followed 100 yards later by a hairpin and the steep final curve to the top of the hill.

It was much quicker to sail around that hairpin in first gear, shifting back to second on exiting while heeled hard over to take the last broad hairpin up to the finish line, and the short finishing straight beneath the large outdoor dining area of the Auerberg Inn, where refreshments awaited.  For me, there would be 199 other motorcycles to await as well, so there was plenty of time to observe other riders making their way speedily or slowly or firmly or wobbly on the last corners, with a few having minor mishaps usually caused by insufficient ground clearance!  Luckily there was plenty of grass on the hillside at that spot. The view was amazing, and a stroll through the forest gave cool respite from the sun.

I was only able to complete two timed runs, with a difference of 1.3 seconds between them, which put me in 5th place of the 200 riders at that point, but travel demands meant I had to miss my third run. Still, the winner of the event, Jürgen Buschkönig on a 1933 Rudge 500GP, had a total difference of only .72 seconds between 3 runs!  Now that’s consistent.  Winning wasn’t my goal, riding the Crocodile was, and that was a very special experience indeed. It isn’t every day one is invited to ride an ultra-rare and storied 90-year old Grand Prix racer, and the Crocodile proved delightful.  It’s a mystery why Sunbeam didn’t push forward with overhead-camshaft development, although the Crocodile proved no faster than its pushrod stablemates. It took Eugene Goodman at Velocette to point a stroboscope at a running KSS engine in 1926, before the aha moment, and the realization that pushrod engines rely on valve float for good breathing, while an OHC motor needed a different cam shape to release the power potential inherent in better valve control. After that, Velocettes won 3 Isle of Man Junior TTs in a row, and a pushrod-engined motorcycle never again won that race, nor the Senior TT after 1930.  It could have been Sunbeam in the mix too, as a worthy rival of Norton, but there you have it – we’re left with a few beautiful examples of the Crocodile to appreciate the effort.

The Auerberg Klassik is a delightful event, with real history, having been originally run from 1967 to 1987.  One of the event’s 5 organizers, Hermann Köpf (of Brummm Chronicles – an excellent magazine of motorcycle photography), grew up in the nearby village – Bernbueren.  Working with his team members, it took little convincing to bring the village back on board for such an event, and while the first Klassik event in 2017 was rainy, it still drew 5000 people to this tiny country village for the weekend.  This year attendance was over 10,000, with festivities in the town square, and spectators lined up the mountain course, giving full-throated approval to the proceedings.  It was the first time I’ve experienced such enthusiastic support of a vintage event from spectators, organizers, and locals, creating an extremely friendly vibe with small-town charm.

For a ‘local’ vintage motorcycle hillclimb, the attendance at the Auerberg Klassik was enormous, and provided a much-needed injection of optimism for the old bike scene. It wasn’t a hipster crowd, there was no ancillary skating or surfing contest, and the sponsors did not dominate the visual landscape.  It was locals making cakes and pastries, serving beer, and making sure everyone was having a pleasant weekend, which gave the event a genuine feeling, and that seemed organic to the life of the village.  Simply fantastic: I congratulate the organizers on their success, and long may it continue.

Many thanks to the Hockenheim Museum collection for allowing this precious machine to be used as the maker intended.  I was honored to be invited to twist its throttle, and share the unique sound of this machine with 10,000 people!  And thanks to the gracious organizers of the Auerberg Klassik, especially Hermann Köpf for poking me to attend. I wish you all success in the future.