[March] 2011, Welshpool, Powys.
Friends and lifelong bikers Stephen, Nick & Karl are discussing impending old age in their lunch break. Steve and Nick are staring down the barrel of their half-century. Karl is ten years their junior, but not relishing leaving his thirties any more than his workmates are looking forward to being fifty.
“We should do something…. I dunno, something to do with bikes – an epic journey or something.” “How about… riding across India on Royal Enfields?” “Rimini on Lambrettas?” Discussion ensues, with the magnitude of the undertaking ruling out the former suggestion, and the fact that nobody is much into scooters does for the latter.
“Tell you what – we could go to Bonneville Speed Week and break some records…”
August 2013, Bonneville Salt Flats, Utah.
Friends and lifelong bikers Stephen, Nick and Karl (and Steve’s son Chris) are packing two rather special BSA Bantams back in to a rented U-Haul trailer, having just set or broken three land speed records in as many days at the 65th Annual Speed Week. It’s time to start the long trek home, everyone’s knackered, the rented RV that’s been home to Team [Rooster Booster] for the last ten days is encrusted with salt and judging by the pervasive odour towards the back of the cabin, the sewage tank is overdue for emptying, but right now nobody cares. The dream has been made real, the records are theirs.
Making the dream real had not been easy. After that only-half-serious lunchtime discussion 30 odd months ago, the project had tested the resolve of the team on many occasions, and caused something of a shortage of midnight oil in mid-Wales. The decision to actually go to the salt followed on from Karl’s acquisition of the SCTA (South California Timing Association) Rule Book, into which he immersed himself for several days before announcing that the vintage 125cc motorcycle class looked like a promising category for what still seemed like a rather unlikely adventure. Certain ground-rules had already been established. Although sponsorships would be sought (and ultimately found) the budget was of necessity limited. Membership of the 200mph club sounded attractive, but the entry fees tend to be substantial, so a smaller capacity class was where Karl was concentrating his research.
The bike would have to be British, and preferably a well-known model to appeal to sponsors and enthusiasts alike. The Bantam seemed an obvious choice, and it was, except for the fact that none of the team members knew much about two strokes. Nick had had a Bantam as a field bike in his youth, but like most 12 year olds, he was more interested in thrashing it to within an inch of its life than learning about squish clearances or the niceties of loop scavenging. Not to worry they thought– there’s plenty of Bantam experts around...
After further forays into the SCTA rule book, it was decided to run two bikes.
One would be ridden by Stephen and would complete in the APS-VG 125
Class (A[?] Partially Streamlined – Vintage Gasoline 125 cc) and Karl would
compete in MPS-VG 125 (M [check]). The main difference between the bikes
would be the frames. Karl’s essentially standard, Stephen’s an exquisite one-off
double cradle from Metal Malarkey.
Both bikes would run full fairings and engines of similar specification. Ah yes -
the engines. While Nick set about the mainly thankless task of getting sponsors
on board, Stephen and Karl prepared to open the can of worms marked “highly
tuned two strokes”.
Making Bantams go quick was a well-documented British pastime even before Nick was riding his round a muddy field, but there was a snag. The Bonneville bikes had to remain as 125s, and the class rules were anything but friendly toward small high revving two strokes. The cylinder barrels had to remain original, the crankcases also, and the factory ignition type must be used. Not the end of the world if you’re running a low revving supercharged V8 – but a bit more of a problem for the Roosters. Modification of the original castings is permitted, and although points ignition was mandated, the points themselves could be changed. Karl was by now something of an expert on port timing, gas flow, and compression ratios, and Stephen was itching to put his considerable skills as a time-served toolmaker to good use. He didn’t have to wait long…
Where red-hot Bantams are concerned, the recommended procedure for best
results is to sling the stock barrel in a skip, but as that wasn’t an option major
surgery had to be performed. To allow the port sizes that Karl wanted, metal
had to be added to areas around the exhaust and transfer ports, and new inlet
stubs attached. To keep the engines cool the original finning was largely removed
and a huge aluminium finned collar hand-machined by Steve was shrunk onto the
barrels. The crankcases were heavily modified around the transfer ports using a
tig welder and lots of filler rod, and new cylinder heads were procured. The
exacting task of porting, gas-flowing and matching the barrels and crankcases
was entrusted to stroker guru Mark Broadhurst, and the exotic looking expansion
chambers were designed and welded up by [??]. The primary drives and gearboxes
were left essentially stock with beefed up clutches. The hybrid ignition systems use
RD400 points and cams from an obscure Volvo Penta outboard motor.
All they needed now were crankshafts, and Stephen was also the man to solve that
particular issue. Many hours of CAD design was followed by CNC machining, stress
relieving, more CNC and finally precision grinding and assembly, until two of the
finest Bantam cranks you will ever see were ready to install.
By now it was [April 2013] and time was compressing at an alarming rate. There was just time to get the engines installed in the chassis and onto the dyno for a few pulls before packing them up for shipment to the USA. Although there was no time to do much more than twiddle the ignition timing a bit and do a few plug-chops, the dyno time was a cause for some cautious celebration. [18] bhp at just under 11000rpm suggested that all the hard work had been worth it. Considering the gradient of the learning curve, a power output of three times that of the standard engine was firmly in wildest dream territory.
Getting the bikes to the salt was another project in itself - Burt Munro had an easier time according to Nick but as the first day of the 65th Annual Bonneville Speed Week dawned, they were there. Bonneville… thanks to Johnny Allen’s bravery and Edward Turner’s opportunism the word has an almost unequalled resonance for bikers, and the place is on everyone’s bucket list. It deserves to be. Although we’ve all seen the pictures, the first time you see the sun come up over the vast expanse of salt to illuminate the queue of hotrods, lakesters, streamliners and bikes waiting patiently in the fire-up lanes to take advantage of the denser morning air, there will be a lump in your throat. It’s a special place – if the goal was just to get here and run, it isn’t any more. Now it’s to get your name in the record books.
First time up the four mile ‘rookie’ course, the bikes just wouldn’t run. The 18bhp had somehow morphed into next-to-nothing halfway across the Atlantic. In fact they were still in rude health at that point in their journey, but now they were on a dry lake 4200’ above sea level with the mercury busting 40deg C, and the boys were discovering the hard way what an evil mistress the salt can be. If you have a several thousand horses straining at the leash, and you want to go very fast indeed, Bonneville is a great place to do so. It’s very very big, and very very flat. If you have a BSA Bantam though, even a very trick one, you’re better off in the car park of your local ASDA. The altitude means the air is thin at the best of times (at dawn) and by mid-morning the best of times are long gone and the temperature has increased the effective altitude to over 7000’. That's not too much of a problem for machines running oxygen-laden funny fuel or massive boost levels, but for a little stroker gulping 125cc of what passes for air and mixing it with plain-vanilla gasoline, it’s bad news. Not quite as much of a problem as the salt itself though. Imagine riding on a mixture of compacted snow and sugar and you’re getting close. Low friction it isn’t. Whatever speeds the bikes were to achieve would be well down on their potential sea-level tarmac performance.
After some minor panicking, rational thought suggested the thinner air was richening the mixture, so as a quick check the air filters were binned and replaced with the gauze from some hastily sourced tea strainers. It worked so well the jets were left untouched. Now the engines would rev. Rev well enough to seize up in fact. Still – hot strokers always seize at first don’t they? More than a grain of truth in that, but the remedy is the same either way. Top end strip, break out the flex hone, the wet & dry and the Scotchbrite. When the engines were buttoned up again the roosters started to show their mettle. Gearing was tweaked, but not much else was changed as Stephen and Karl edged the bikes into their sweet spots. The 3 speed boxes were roundly cursed – the combination of narrow power bands and a high-friction surface meant that getting back on the pipe after shifting into top was a struggle that had not been apparent on the dyno. The clutches came to the rescue, withstanding the brutal slipping that was the only remedy on offer.
The speeds continued to climb and the records tumbled.
In a final flourish, Stephen exited the measured mile at a
smidgeon under 89mph. The records achieved were:
[LIST - show previous for comparison] The third record
[F] was Karl stamping his authority on the proceedings by
taking the ‘fuel’ record on a gasoline powered bike. A bit
like Everest in 1953, it was there, so he added it to the tally.
Well – you would, wouldn’t you?
Metal Malarkey Bonneville Bantam "Special"
