BSA M20 & M21 Pros
Mechanicals: Simple, but some head-scratching required.
Handling: Surprisingly good. You can throw these around.
Forks: Tele models are predictable. Girder bikes are crude.
Starting: Sorted bikes fire-up with a gentle nod and a prod.
Spares: Still enough parts around to keep them rolling.
MOT: Not required any more. No road tax required either.
Looks:. Classic Brit single appeal. Olde worlde charm.
Sound: BSA M20/M21 sidevalves chuff very satisfyingly.
Clutch: Fairly light and smooth in action.
Resale: Military bikes in high demand. Less so civvy iron.
Magneto ignition: Separates the sparks from the electrics.
Re-enactment: Dress like a despatch rider. Fun for some.
Investment: WM20 military bikes hold their values well.
Brakes: Later post-war M21s have good front stoppers.
Tough: Solidly built. All steel and cast aluminium.
Engine: Strong. Exhaust valves need care and love.
BSA M20 & M21 Cons
Economy: Poor. 40-45mpg at cruising speeds.
Oil: Most leak a little from one or more joints. Manageable.
Performance: 45-50mph cruising. Flat out at 60. Maybe.
Brakes: Generally poor, but careful set-up helps.
Acceleration: Hopeless. 0-50mph eventually.
Maintenance: Regular lovelorn tinkering required.
Tools: Whitworth spanners. Some special items needed.
Comfort: Pillions will hate it. Riders will merely endure.
Lighting: 6-volt electrics. Feeble all round.
Gearbox: Prone to leaks. Demands slow changes.
Carburettor: Standard Amal 276 likes to sneeze fuel.
Sidestand: Not on WW2 or pre-war bikes.
Horn: Altettes need good set-up. Otherwise feeble toot.
Sparks: Learn to set ignition points. Not too hard.
Storage: They wet-sump and prefer daily exercise.
[Okay, tell me more about BSA M20s/M21s...]