B66 BSA - Get your kicks on the B66

15 March 2017
Story Andrew Wilson Photos Andrew Wilson, Jim Scaysbrook, Sue Scaysbrook

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. But in between, the midnight oil was again burning down under in Doug’s shed. 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, 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 Shannons Club bikes. Again, a very special, one-off machine.

But Doug was far from finished there. 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. And so, there, in the middle of the shop, the final bits and pieces were slotting together to complete the masterpiece.

So, name first – Doug is calling both 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. The cams are one-offs, but based on B-series profiles and using scrambles Gold Star timing.. 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.

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.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, 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.

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.

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. 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. 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.

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.