BSA B50T

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BSA-B50SS-71.jpg
BSA B50T
Manufacturer
BSA
Production 1971 (5700 units)
Class Enduro
Engine
Four stroke, single cylinder, OHV, 2 valve
Bore / Stroke 83.8mm x 83.8mm
Compression ratio 10.0:1
Top Speed B50SS: 160 km/h / 99 mph
B50T & MX: 145 km/h / 90 mph
Horsepower 34.06 HP (25.4 KW) @ 6200RPM
Torque 28.03 ft/lbs (38.0 Nm) @ 5000RPM
Ignition Lucas RM21
Spark Plug Champion N4
Battery 12V
Transmission 4 Speed
Frame Welded frame with larger diameter top tube for strength
Suspension Front: Telescopic forks
Rear: Swing arm, 2 shocks wiith dampers
Brakes Front: 8 in. drum, leading shoewith snail cam shoe adjustment
Rear: 7 in. drum with floating cams
Front Tire SS & MX: 3.25x18
Trials: 3.00x20
Rear Tire SS & MX: 3.5x18
Trials: 4.00x19
Wheelbase 1372 mm / 54 in.
Seat Height 813 mm / 32 in.
Weight B50SS & MX: 140.6 kg / 310 lbs B50 T: 135.0 kg / 298 lbs (dry), 184 kg / 406 lbs (wet)
Oil Capacity 3.4 L / 6 pints / 0.9 US gal
Fuel Capacity UK: 18.2 L / 4.8 US gal US: 9.1 L / 2.4 US gal
Manuals Service Manual

The BSA B50 T was a air-cooled, four-stroke, single cylinder, OHV Trial motorcycle produced by BSA in 1971. Max torque was 28.03 ft/lbs (38.0 Nm) @ 5000 RPM. Claimed horsepower was 34.06 HP (25.4 KW) @ 6200 RPM. It could reach a top speed of B50SS: 160 km/h / 99 mph B50T & MX: 145 km/h / 90 mph.

Engine[edit]

The engine was a Air cooled cooled Four stroke, single cylinder, OHV, 2 valve. The engine featured a 10.0:1 compression ratio.

Drive[edit]

Power was moderated via the Multi-plate, wet, cable operated.

Chassis[edit]

It came with a SS & MX: 3.25 x 18 in. T: 3.00 x 20 in. Trials front tire and a SS & MX: 3.5 x 18 in. T: 4.00 x 19 in. Trials rear tire. Stopping was achieved via 8 in. drum, leading shoewith snail cam shoe adjustment in the front and a 7 in. drum with floating cams in the rear. The front suspension was a Telescopic forks while the rear was equipped with a Swing arm, 2 shocks wiith dampers. The B50T was fitted with a UK: 18.2 L / 4.8 US gal US: 9.1 L / 2.4 US gal fuel tank. The bike weighed just B50SS & MX: 140.6 kg / 310 lbs B50 T: 135.0 kg / 298 lbs. The wheelbase was 1372 mm / 54 in. long.


1971 - 1973 BSA B50 T[edit]

1971 - 1973 BSA B50 T 1971 - 1973 BSA B50 T

The 1971 BSA B50 T has, at its heart, an air-cooled, four-stroke, 499cc, single cylinder powerplant mated to a four-speed manual transmission and can produce 34 horsepower and 38 Nm of torque. This two-wheeler also comes with feature such as laced wheels, a telescopic front fork, dual shocks in the rear, drum brakes on both the front and the rear wheels, a dual seat, passenger grab rails, a small, round headlight, a small fuel tank and mid-mounted foot pegs.

Photos[edit]

Overview[edit]

B50SS[edit]

Of the 5,700 or so that were built, survival rates are low. Which is partly why today the B50 is as rare as a priest with a clean conscience. It’s not the easiest bike to live with. And it needs a good dose of retro-engineering to get the very best from it. But you can be sure that ownership of one will, at least, never be dull. But was it ever worth the hallowed Gold Star name that was bestowed upon it? It’s a debate that still rages. Overall, these are great little BSA singles. You wouldn’t want to ride two-up on one—unless most of your journeys were shorter rather than longer. But as a solo mount, it’s a stylish thumper with a hidden chunk of lead in its glove. Remember to duck.


B50T Victor[edit]

1. The unit single crankcases were originally designed for a 250cc engine. Accordingly, the B50 pressures beneath the piston are considerable and put a huge load on gaskets and seals. A timed breather is vital to keep the crankcase at negative, or at least neutral, pressure. Well-fitting mating surfaces are essential if you want to keep the oil in rather than out. 2. Poor handling is often attributed to the swinging arm bearings. These pivot on needle rollers and need plenty of grease to avoid seizure. Raise the bike and check for play. Replacement is straightforward. 3. The extra torque of the B50 means that clutches are prone to slippage and so need need to be kept in tip-top shape. Solutions include an extra friction plate, an extra steel plate, stronger clutch springs, and an alloy pressure plate. 4. The bore can be opened up to 90mm giving 572cc for extra stomp. You’ll also need to gas flow and fit a larger (32mm) carb. 5. Ignition coils were always weak leading to poor starting, irregular tickover, and misfires. Fit the best quality replacements you can afford along with a new condenser and quality plug lead. 6. Whilst good enough for general use, high performance B50s will require an upgraded crankpin such as Alpha. A Carillo conrod is also highly recommended. 7. Rocker boxes are prone to leakage which can be sorted by careful linishing. 8. Poor crankcase scavenging seems to affect some bikes more than others, and is said to be due sometimes to mismatched sump covers blocking oil pick-up holes. B50MX Introduced in 1971, the B50MX (Motocross) was the last competition motorcycle announced by BSA, just as the company’s efforts came to a close. Developed through the great success of the BSA ‘works’ machines in motocross, and using bikes based on the B44 Victor, the B50MX offered a strong and powerful 500cc engine. A new chassis design which saw the introduction of an oilbearing frame and its extreme slimline aesthetic that was enhanced by a beautiful tucked-in exhaust system ensured this machine’s place in history as it was one of the rarest and most successful BSA MX designs of the period.

Specifications[edit]

Make Model BSA B50SS, B50T, B50 MX
Year 1971 - 73
Production 5700 units
Engine Type Four stroke, single cylinder, OHV, 2 valve
Displacement 499 cc / 30.5 cub in.
Bore X Stroke 84 x 90 mm
Carburettors B50 SS & T Amal R930/62 B50 MX (71-72) Amal R932/18, (73) Amal R932/28
Cooling System Air cooled
Compression 10.0:1
Lubrication Wet sump
Engine Oil SAE 20W/50
Oil Capacity 3.4 L / 6 pints / 0.9 US gal
Exhaust Single, chrome plated
Ignition Lucas RM21
Spark Plug Champion N4
Battery 12V
Starting Kick
Max Power 25 kW / 34 hp @ 6200 rpm
Max Torque 37.9 Nm / 3.86 kgf-m / 28 ft/lb @ 5000 rpm
Clutch Multi-plate, wet, cable operated
Transmission 4 Speed
Final Drive Chain
Frame Welded frame with larger diameter top tube for strength
Front Suspension Telescopic forks
Rear Suspension Swing arm, 2 shocks wiith dampers
Front Brakes 8 in. drum, leading shoewith snail cam shoe adjustment
Rear Brakes 7 in. drum with floating cams
Wheels Steel, spokes
Front Tire SS & MX: 3.25 x 18 in. T: 3.00 x 20 in. Trials
Rear Tire SS & MX: 3.5 x 18 in. T: 4.00 x 19 in. Trials
Dimensions Length: 2159 mm / 85.0 in. Width: 737 mm / 29.0 in. Height: 1105 mm / 43.5 in
Wheelbase 1372 mm / 54 in.
Ground Clearance SS & MX: 178 mm / 7 in. T: 191 mm / 7.5 in.
Seat Height 813 mm / 32 in.
Dry Weight B50SS & MX: 140.6 kg / 310 lbs B50 T: 135.0 kg / 298 lbs
Wet Weight 184 kg / 406 lbs
Fuel Capacity UK: 18.2 L / 4.8 US gal US: 9.1 L / 2.4 US gal
Standing 0 - 100 Km/h / 62 Mph 7.4 sec (B50SS model)
Top Speed B50SS: 160 km/h / 99 mph B50T & MX: 145 km/h / 90 mph
Review Sump publishing

External Links[edit]