BSA B66: Get your kicks on the B66

Bike Profile

Doug Fraser's Empire Twin, a plausible name that BSA bracketed, but never actually used. This one is specifically identified as a B66, given its use of B33 top ends, albeit heavily modified.

In OBA 10 we featured Doug Fraser’s remarkable Empire Twin. Now it has a brother…the B66. It has to be shared right here and right now: the B66 is the best motorcycle BSA never made, and if they had produced it, then it would have been the most sought-after model in their whole catalogue. This unique, astonishing machine is an absolute belter in every way, and its story is an inspiration to every bloke (and blokess) in a shed the world over.

The man behind it is Doug Fraser, from Melbourne. I first met Doug back in 2006, and we’ve been firm friends ever since. Back then, I had the chance to ride Doug’s delightful 550cc Gold Star and to appreciate the subtle improvements that Doug had made, all the time guided by the principle of what the factory might plausibly have done if they’d had the investment and sufficiently enlightened leadership. Doug subsequently brought the Goldie to the UK, and I had the chance to ride it much more extensively in Scotland and on the Isle of Man, appreciating even more its flair and ability to excite. But in between, the midnight oil was again burning down under in Doug’s shed (or, more accurately, professional workshop for his heavy electrical engineering business). Something very special was happening, as Doug took his concept of “what the BSA factory might have done…” one giant leap forward.

BSA had some notable big v-twins pre-war, the model E and model G (they weren’t big on jazzy names back then). But post-war, the future lay in singles and the new parallel A7 and A10 twins. In his retrospective re-write of BSA history, Doug was able to exploit the same principle that so many manufacturers have done before: that the easiest way to make a big twin is to make a V-engine more-or-less from existing singles. The result was the rigid-rear, girder-front M46 Empire Twin that’s already been featured in OBA. Again, a very special, one-off machine that I also recently got a chance to try out on the fantastic roads of New Zealand.

But Doug was far from finished there, as he hinted while kindly inviting Elaine and me to spend a week with his family in Melbourne en-route to the BSA International rally in New Zealand, in early February 2010. He’d been muttering on email about a “little project” he’d been working on that he wanted to show me, and I knew from previous experience that it would be something interesting, engaging and fun. I also knew that Doug had got at least one extra pair of crankcases cast up when the M46 was in progress. So, I did have a bit of an inkling, and it was with increasing anticipation that I piloted Doug’s aforementioned Gold Star Special down from Melbourne to the workshop in Carrum Downs. Doug had left home even earlier than normal that day, just to put some finishing touches to the project. And so, there, in the middle of the shop, the final bits and pieces were slotting together to complete the masterpiece.

The B66 looks exactly right, with starter motor a welcome addition and well hidden.

So, name first – Doug is calling both (he has no plans right now for any more) his V-twins Empire Twin, a plausible name that BSA bracketed, but never actually used. This one is specifically identified as a B66, given its use of B33 top ends, albeit heavily modified. Take a look at the crankcase, and you’ll see the engine number CB66-101, mimicking the slightly woolly year prefix scheme that the factory employed. As you stare again and again at this machine, from every angle it looks like a factory motorcycle, with an integrity of design that makes you think there must have been dozens of prototypes and years of evolution. And that’s true of some of the parts, but the machine itself really was designed in Doug’s head, more or less.

So, what’s inside it? Well, the heart is two M20 drive-side flywheels, united by a Harley-Davidson Sportster 20mm crankpin. That means the benefit of four roller bearings to support the crank, which gives a more-than-adequate margin for some adventurous use. Anyone who’s tried it knows how hard it is to true up an off-the-shelf built-up crank, let alone one that’s had one-off machining. You begin to see why Doug sometimes literally slept in the workshop so as to maximise the time he could spend on his magnum opus. On this pin, sits a standard H-D forked conrod pair, making any future overhauls a simple matter of pulling standard parts. That brings us neatly to the crankcase, Doug’s own design and cast from moulds he made up. The machining was clearly critical, and had to be done very carefully to minimise the possibility of a fatal write-off. The cylinder angle they provide is 50-degrees, giving a link back to earlier factory BSAs as well as the most compact motor possible. This was a vital parameter in the quest to retain standard frame geometry. As you can see, Doug not only achieved the technical requirements, he also arrived at a shape that looks just right, as if it had come straight out of Armoury Road. This is a far-from-trivial point, and one that comes up again and again on the B66. One part of this engine that required the least work was the oiling system – the twin gear pump on the B-series singles is a very sound design, and Doug was able just to carry it over without any modification. Right now, it’s running absolutely as standard, but Doug will fit a return-side filter (a Rocket-3/Trident element in his own machined housing) in due course. This isn’t so vital as on the plain-bearing twins and triples, but still well worth it. The cams are one-offs, but based on B-series profiles and using scrambles Gold Star timing. Doug roughed them up and then had them ground up and hardened locally. So, how about the top end? Well, as I’ve mentioned it is basically B33-sourced, so the trademark and very handsome cricket-bat pushrod tunnels come for free. They look great on the singles, and even better here. But little else is standard up top, for a start the barrels are Doug’s own alloy castings, and with their bore of 88mm combined with the M20-derived stroke of 94mm gives a whopping 1140cc total displacement. The forged pistons give a high-ish 9.25:1 compression ratio, but the engine shows no signs of distress on that, front. The B33 heads are heavily modified to open the inlets ports out to 34mm and make them point the correct way – lots of machining and welding there. There’s also a lot of work in relocating the oil drain tappings to the new-found appropriate low spots on the V-twin. Oh, and big valves as well, just for good measure. Feeding into these inlet ports are a pair of Mk2 Amal concentrics, with beautifully-crafted pipework connecting into pancake air filters. Doug’s philosophy on usability, as well as the guiding principle of what BSA would have done, makes filters essential. What’s really neat about these is how he’s managed to package the front one so it doesn’t stick out into the leg space below the curvaceous Lyta tank. Completing the picture on the timing side, Doug’s own housing contains an auto-advance and conventional points setup. Since the machine has electric start, it runs 6-volt coils with ballast resistors that are bypassed during starting – conventional practice on cars before all-electronic systems became common.

Thumping great V-twin has bags of torque yet is a willing revver. The five-speed Triumph gearbox is a delight to use.

Over on the drive side, it’s a mixture of the conventional and novel. The Lucas alternator (charging via a normal bridge rectifier and Zener diode) and single-row primary are familiar, but no production BSA motorcycle ever had the electric start provided here (leaving aside some Sunbeam scooter models). This one uses a Yamaha motor with an integral 3:1 epicyclic reduction, and 2:1 reduction via a chain onto a sprag clutch out of a car automatic transmission mounted on the crank. This keeps the sprag well-lubricated, essential for its longevity. The art (literally) here though is to modify the chaincase so that it looks meant, not like the old Spam tin that ends up covering the primary on so many specials. Take a good look at this case – you’ll never spot the welds, nor see any other evidence that makes it look anything other than a factory job. As well as the aforementioned ballast resistor bypass, the starter also benefits from the B33 standard valve lifters in getting the 1140cc lump spinning.

Bringing up the rear is a gearbox similar to Doug’s Goldie – a pre-unit Triumph shell modified to take a T140V 5-speed cluster, complete with 7-plate, 4-spring clutch. As should be no surprise by now, Doug invested some of the mods to the case and cover simply to make its shape more complementary to the BSA frame, with huge success.

On now to the frame itself. It started life as an A10, and Doug had to fit new downtubes to make the V-twin fit. Retaining the standard wheelbase and geometry was a triumph (oops!), for in some bodged-up marriages of other v-twins with BSA frames, up to 4” has had to be let into the frame top and bottom to squeeze those interlopers in. Up front sit forks and twin discs originally from a Rob North R3 race bike, with the necessary lights, switches and indicators grafted on – again, all plausible things for a factory machine. A Bonnie 750 mudguard finishes it off perfectly.

In the rear, Doug has used a BSA conical hub – but went the extra mile in machining up a Gold Star style finned ring that remains removable to allow the sprocket to be changed. Again, an astonishing dedication to completeness, and a touch that sits so well with the Goldie rear mudguard.

Left: Triumph conical rear hub, and the obligatory Goldie silencer make for a tidy rear end. Right: Front forks and disc came from a Rob North Trident.

Two final major items really finish off this machine, in grand style. The first is the Lyta tank, that Doug had to cut open and build a complete new base for. It had to fit over the coils, heads and all the framework underneath, which it does beautifully. The final piece is the intricate two-into-one exhaust system. Doug had the stainless Goldie-style silencer made for him, but the pipes are his own, fabricated from umpteen sections welded together and painstakingly dressed down until the joins become invisible and the whole thing looks absolutely right for the machine. I just don’t know how Doug managed to achieve the front pipe running inside the frame downtube, but it’s a line that not only makes the pipe neat, it gives a unique look to the finished motorcycle.

Rider’s eye-view is uncluttered and neat.

Now, a lot of specials are just well-engineered (or even poorly so) ornaments, containing unforeseen but fatal flaws that render them unusable for more than a few miles up the road. With that in mind, it’s time to see how the B66 performs. Given its uniqueness, and the thousands of hours Doug had just put into it, I was of course a little nervous at the thought of taking the latest Empire Twin out. But the chance was just too compelling to dwell on any negatives, plus I had Doug insisting that I should take it for a proper belt, not least so he could see it go for himself. So, on a hot and sunny Victorian February day we rolled the machine out, as Doug fired up the Goldie to accompany me. The charging system wasn’t fully debugged, so in deference to the battery, the first start was by foot, and easy enough with the Triumph kickstart gearing. As you sit on the machine, everything feels normal and familiar, and since nothing sticks out past the knee recesses on the beautiful Lyta tank, there’s little clue initially that this is anything other than a normal Beeza single. That is, until you ease out onto the side roads and give it a bit of stick. There are of course faster bikes and there are smoother ones, but the way that the B66 grabs the horizon and fetches it closer with just the right degree of presence is truly a delight. There’s no other way to say it. Mainly because I hadn’t a clue where we were going, I initially tailed Doug out onto the freeway. Once out on the open road, there was just no holding this machine back. A discreet wave from Doug up ahead seemed to pass from him directly to the B66, rather than via its rider. With a growl and a roar, the machine surged forward and thundered past the Goldie, in one smooth, effortless motion. Doug doesn’t like to guess at horsepower, and he might one day get round to having it measured, but for now let’s just describe it as several notches above adequate. The short lever on the T140 box needs a good prod, but the travel is so short that you can run up and down the ratios with ease – not that you have to with 1140cc up top. This is when you really feel the benefits of the immense effort to keep the frame geometry and dimensions intact. The machine handles just like any other well-sorted BSA, in other words – very well indeed. It tracks straight and true, but you can flick it from line to line and into corners with supreme ease. Then there’s the brakes – those twin Lockheed discs are light, powerful and with more than enough in reserve for repeated high-speed stops. The conical hub rear was always a good brake, and no less so here. So, we spent the whole day having fun on the roads in and around the city, and of course laying up at the odd café to bask in the glory of it all. Later on that day, Doug took the B66 on a night ride over to the BSA club meeting on the other side of the city, with Elaine on pillion, as I tailed on the Gold Star. Never did a machine look so utterly graceful, exciting and sorted as the big V-twin, burbling and roaring up the freeways and back streets into the darkness.

So, all-in-all, it’s almost impossible to believe that a motorcycle this competent in every dimension could be a one-off special. Even more incredible is the way it performed literally hours after its final assembly. Incredible, that is, if the constructor had been anyone other than Doug Fraser. There are many people out there with engineering skill, plenty of others with imagination. But when huge amounts of both talents come together in one person, then unbelievably great things happen. Motorcycles like the B66 Empire Twin happen.

Such was my haste to get out of the pits and onto the track, I forget to do up my right boot, for which I was subsequently black flagged!

A blast around Broadford with Jim Scaysbrook

Amid the frantic activity in the pits on Easter Saturday morning at the recent Honda Broadford Bike Bonanza, I spied Doug Fraser warming up his extremely rapid Norton Rotary racer. “Have a look at this”, he beckoned to me, indicating something inside the garage. And there it was – the B66. “Take it out for a spin, there’s a track session on now,” he said, wheeling the bike out into pit lane – the briefing over! Grabbing my helmet and gloves I jumped aboard as Doug thumbed the electric starter and the big twin burbled into life. “It really gets going about 6,000 rpm. It’s got a few hundred miles on it now, so don’t be afraid to give it a bit of stick.” And with that, I was on my own, entrusted with this priceless and totally unique piece of kit.

Fifteen minutes later I was back, completely in love. So smitten was I that I asked as politely (but firmly) as I could for another ride the next day, to which Doug readily agreed. This bike is simply brilliant to ride, and it’s quick, pulling a genuine 100 mph on Broadford’s top straight and whistling past all manner of other machines out there in the Road Bike session. Not wanting to risk any internal damage, I didn’t take it past 6,000 rpm in any gear, at which point it was spinning away sweetly. Such is the torque that it doesn’t need massive revs, and not once did I find myself in the wrong gear – it just pulls away as you snick thought the excellent gearbox. And the B66 handles at least as well as any duplex frame BSA I have ever ridden. The only criticism was that the front forks were too soft, a point that Doug is well aware of, having stiffened up the rear to cope with the extra weight but not having the required stronger front springs on hand for the weekend. Still, that will be a minor adjustment for a bloke who has created this phenomenal machine from scratch. Put it in production Doug – I want one!

Story: Andrew Wilson • Photos: Andrew Wilson, Jim Scaysbrook, Sue Scaysbrook

OBA Issue 20
This article first appeared in Old Bike Australasia Issue No.20.