The BSA B40 is a cool little classic with a deservedly poor reputation, yet that didn’t stop it from being an incredibly popular machine. It served as one of the primary replacements for the post-WW2 BSA M20’s and Matchless GL3’s. The B40 would see ample use by the British Armed Forces who ordered more than 3,000 units, including 141 for the Royal Air Force and 34 for the Royal Navy. Other military forces including those of Australia, Denmark, and Jordan also placed orders for the B40. Like the vast majority of military scoots, the B40 was primarily a road-goer that had limited off-road capabilities.
Powering the B40 was an 343cc OHV single that made an underwhelming 20hp at 7,000rpm. The bike had a four-speed gearbox, full-cradle tubular welded frame, telescopic fork, a top speed of around 65 mph, and a wet weight of 364 lbs. Though many devoted BSA customers purchased the 343cc model and BSA touted it as a “modern motorcycle” upon its release, lots of riders thought the B40 was born out of half-measures and cutting corners. To fully understand just why this is and where BSA went wrong, it helps to have a decent grasp on the technological advancements of late-1950’s motorcycling.
In 1958, BSA launched the all new quarter-liter C15 model. Thought it was reportedly a poor-handling, poor-stopping, and poorly-outfitted machine, it still sold relatively well. Meanwhile, Japan was busy innovating and pushing the envelope of what was possible. Pops Yoshimura had just blessed the motorcycle world with his high-revving (13,000rpm) double overhead cam, 125cc twin Honda which Mike Hailwood would pilot to victory at the TT. His eighth-liter racer was an obvious sign BSA needed to step its game up. This was accomplished (or attempted at least) by boring the 67mm C15 to 79mm, resulting in the B40, a slightly larger updated version of the C15 that failed to address many of the 250’s shortcomings.
The already shoddy gearbox and clutch from the C15 made their way onto the B40, as did the less-than-impressive bottom-half of the engine. To increase reliability, BSA reduced the compression ratio to 7:1. The suspension was also nothing to write home about as the rear shocks did not allow for any adjustment and only compression damping was adjustable up front. In a nutshell, the B40 was born out of BSA looking for areas to save on cost with little concern for innovation or reliability. Frank Melling of MotoUSA and the organizer of the British vintage motorcycle event, Thundersprint, called the B40 “A disgrace to what, at the time, was one of the world’s leading motorcycle manufacturers.” Had it not been for the massive military orders that were placed, the B40 would have been an objective failure.
Despite its aforementioned shortcomings, the B40 does have some charming old-school qualities once you look past its performance problems. It’s a cool looking vintage Brit bike that can be improved via updates to make it a better performing and more reliable bike. This particular 1964 B40 example underwent a ground-up restoration about eight years ago, though it has since only had covered 100 miles. The engine and frame have matching numbers and the seller made a few upgrades while still putting some effort into restoring the bike to near its original appearance. This includes its redone factory paint job in red, which was one of three colors the B40 came in (as well as Defense-Force Green and Plumb Black).
The fenders on this example are from a later 1971 model, and the electrical system has been converted to a 12 volt unit with a new dry cell battery, replacing the original 6-volt setup. Frank Melling compared the stock lighting’s lumen output to that of “an arthritic glow-worm,” so this is a fairly crucial upgrade to make if you ever plan on riding after sundown. Another important upgrade came in the form of a NOS carb from 1965 which the seller says is not only markedly easier to tune, but is far more efficient as well (original carb is included in the sale). Also included in the sale is a multitude of books including the original manual and registration, as well as a set of Whitworth tools which is important because the B40 is not metric or standard.
You can find this fully restored 1964 BSA B40 for sale here on Craigslist in Woodstock, New York with a price of $3,750.