BSA SPITFIRE
After suffering heavy damage in action, this example of BSA’S ultimate sports twin has enjoyed some serious rejuvenation
Rejuvenated and returned to the road after throwing a rod
When Jon Jolley’s uncle, Bob Price, bought a BSA A65 Spitfire brand new back in the late ’60s, the bike made a big impression on the young Jon. “Uncle Bob used to take me out on the back,” he explains. “When I first got into bikes, A10s were my thing, but my uncle was always trying to get me to buy an A65. I had such happy memories of his Spitfire that, when the chance to buy one came up, I bought it; it’s now in the little showroom at the front of SRM’S industrial unit. When I got offered this one in 2003, I bought it, too. I knew it needed a bit of work, though.” ‘A bit of work’ is something of an understatement. A rod had snapped during a high-speed motorway run and the remnants were fired through the front of the crankcases. “Mercifully, the previous owner – who was riding it with his wife on the pillion – was able to coast in to the hard shoulder without incident or injury,” says Jon. “Apparently, his wife – an experienced lady when it came to British classics – just looked down at it and said: ‘I don’t suppose you’ll be getting this going again at the side of the road’. If he’d managed to do that, he could have had my job.”
After deciding against a costly engine rebuild, the owner offered the bike to Jon as a project – and he eagerly took it on. “I had a few ideas I wanted to try out on it,” he explains. “Because the original engine was basically scrap, I didn’t feel any guilt about modifying what is quite a rare bike. So I found some replacement crankcases from a later 1969-70 A65 – the benefit of using later cases is that they have larger in barrel studs [the earlier barrel studs are in] – and they’re machined to accept an oil pressure switch, which I could use as a take-off for a pressure gauge to check the oiling once the engine was rebuilt.”
Not surprisingly, the original crank was scrap, too. “I wanted to build a bored and stroked engine,” says Jon. “We already produced a big-bore conversion for the A65, based on the old Devimead big-bore kit, so going bigger on the bore size was no problem. But it would be very difficult to stroke an A65 crank. The answer is to modify an A10 crank – which has a longer stroke than the A65 crank anyway – to suit the A65 crankcases. We’ve done
a fair few now. I knew a lot of sidecar racers used A10 cranks in A65 engines, so it was just a question of working out how best to engineer the conversion. In the end, we used our ball-and-needle-roller main bearing conversion – which locates the crankshaft positively in the cases, eliminating end float – and machined off some of the splines on the A10 crank end to accept the A65 alternator, which requires a parallel shaft. The end result gives about 770cc.”
The rest of the engine build again made use of SRM’S BSA parts inventory. “I’ve used our billet conrods, says Jon. “And the head had been modified a little. It’s gas-flowed and I’ve fitted bigger valves, while the inlet ports are machined to accept 32mm Mikuni carburettors. There’s a Spitfire cam, an SRM high-delivery oil pump and, while the gearbox remains standard, it’s got an early Haywood belt primary drive kit.”
The rest of the bike is largely standard MKIV Spitfire – though the swingarm is a later 1969-70 A65 item. “The earlier type of swingarm has Silentbloc bushes,” Jon says. “The later ones have phosphor-bronze bushes with hardened steel inners. They cope better with the extra torque of the bored and stroked engine.”
The rest of the bike is pretty much stock Spitfire, apart from the clocks, which are Smiths electronic instruments. “We approached Smiths to make a batch of A65 pattern clocks and these are the prototypes,” says Jon. “The original magnetic clocks are notoriously unreliable. These have been on the bike since 2009 and work really well. They’re available direct from Smiths (smiths-instruments.co.uk).”
The result of Jon’s labours is a bike that – aside from the Japanese carbs – looks just like a MKIV Spitfire ought to, but should go even better than the original. And that sounds like the recipe for a pretty good bike to me. BSA brought the Spitfire to market in 1966 and it lasted just three years in the catalogue before making way for the new Rocket 3 Triple in 1968. But, for those three years, the Spitfire was the fastest BSA you could buy. Capable of a genuine 120mph on a good day, the Spitfire is, arguably, the ultimate BSA twin.
The first Spitfire (strangely dubbed the MKII; there is no MKI) set the tone for BSA’S top-of-the-range sporting twin. Based on the Lightning, the Spitfire went a step further in terms of performance thanks to high-compression 10.5:1 pistons, a pair of open 1 in Amal GP carburettors with a central, remote float bowl, and a ‘Spitfire’ grind cam. A 190mm front brake in a full-width hub, BSA’S new twin downtube frame and forks featuring both rebound and compression damping (a first for BSA) completed the spec.
By the time the Spitfire reached its MKIII form, for 1967, the all-or-nothing GP carbs had been replaced by a pair of Concentrics with clamp-on filters. The easier starting from hot and better low-speed response from the Concentrics were probably a more than acceptable trade-off for most riders – and many owners of MKII machines had already swapped carbs at their own expense anyway. The final MKIV version of the Spitfire – like Jon’s – is arguably the best of the bunch, with an eight-inch twin-leading-shoe front brake adding a bit of extra stopping power.
Back in the day, though, any version of the Spitfire was pushing the reliability envelope of the A65’s timing-side main bearing bush, which meant engine blow-ups like the one suffered by the previous owner of Jon’s bike were far from unheard of. Today, with the SRM ball-and-roller conversion, end-feed crank modification and high-delivery oil pump, his bike should provide all the performance the Spitfire could offer – plus a little extra thanks to the bigbore kit and A10 crank – without compromising reliability. It’s what the Spitfire should have been.
‘THE ENGINE WAS SCRAP, SO I DIDN’T FEEL GUILTY ABOUT MODIFYING QUITE A RARE BIKE’
There’s certainly nothing subtle about a BSA Spitfire. That huge blood-red tank just demands to be noticed and somehow makes the bike as a whole lot more imposing than the basic A65 on which it’s based. And that means I’m getting a lot of admiring looks as I thread my way through the busy streets of half-term Aberystwyth as I head for the wide, open spaces of mid-wales to really get a feel for the big BSA. Well, the bike is anyway – I’m not sure the slightly damp individual hunched behind the handlebars is turning many heads, but the boom of the big-bore Spitfire certainly is.
A standard Spitfire is more than worthy of note – relatively few of the sporting variant of BSA’S unit-construction Lightning twin were built between 1966 and 1968. Jon Jolley’s MKIV model is even more deserving of a second look, though. It’s a 1968 MKIV for a start – and under 1300 genuine MKIV Spitfires were built that year. While it may not have its original engine, what it does have is an injection of SRM ingenuity hiding behind the familiar unitconstruction BSA outer engine cases. As I know, there’s more to this bike than meets the eye.
Jon’s already explained just how much more – but how much difference will the SRM mods make out on the road? What’s immediately noticeable is just how flexible the engine is. It pulls from nothing, making light work of the ups and downs of just about any road heading inland from SRM’S workshop. But the Spitfire is eager to rev, too – it’s a winning combination. And, although I’m not revving the engine to anything like its limit, I can’t discern any extra parallel-twin vibes from the big-bore lump, either. The 32mm Mikunis fuel perfectly and the bike rips up to 70mph with plenty more to come and feels like it would happily maintain that rate all day – and more. I certainly don’t feel the need for any more than the four ratios supplied by the standard BSA gearbox.
The engine is simply a lovely unit. The added grunt from the extra 120cc capacity makes it an easy bike to maintain a decently fast pace on. I’m following Jon on his tuned A10, who’s riding at a decidedly brisk pace despite the less than perfect conditions – and whatever I lose on entering bends a little more cautiously than him, I can easily make up by rolling open the throttle that bit earlier as the bends unfold. If you’re thinking of rebuilding your A65 engine, Jon’s modifications have got to be worth considering.
The handling of the late-type BSA frame combines with that impressive engine to make riding the Spitfire a real pleasure – whatever the weather. The double-damped forks ride over the ripples and cracks of the A44 in impressive fashion, while the modified Ikon shocks at the rear do the same. The frame and suspension work in unfussy harmony to provide a ride that’s unremarkable for all the right reasons.
Jon reckons the eight-inch tls front brake is possibly the best stopper BSA ever made, and I’m not going to argue with his wealth of experience. Certainly it’s very good, combining sufficient feel to make today’s damp conditions as unthreatening as possible with enough power to get the front end digging in predictably on the steep, twisty downhill sections of road running down the side of the Rheidol Valley from Devil’s Bridge back to the A44. The seven-inch sls rear stopper is just the job for filtering through the traffic in Aberystwyth and for steadying the ship while making hand signals with my right hand. So I have no complaints with the braking system.
Overall, the Spitfire is one very impressive machine. Even without the A10 crank and big-bore barrels, a well-sorted Spitfire (with the SRM crank and main bearing mods) would be a great bike for anyone who likes a British twin. With them, it’s an exceptional bike. Fast, reliable, easy to ride, with bags of character – and a real looker, too. You can’t ask for much more.
‘THE ENGINE PULLS FROM NOTHING BUT IS EAGER TO REV, TOO – A WINNING COMBINATION’