BSA M20

500cc Petrol Class 2

#587 of 5426 overall #29 of 62 BSAs #357 of 2787 other bikes

91.4%

first-time pass rate

2.5%

failed outright

7,746

median miles at test

1,295

MOT tests, 2005–2025

Pass rate over time

first-time pass rate by test year · 2005–2015

The M20's first-time pass rate has fallen 3.2 points since 2005, 97.6% to 94.4%.

Pass rate by mileage

how the M20's first-time pass rate falls with the odometer · class average 84.9%

A low-mileage M20 passes first time 90.9% of the time; by 40k that's 92.8%.

First-time pass rate by odometer reading at test, 10,000-mile bands for this model. Mileage is the strongest reliability signal. See the full curve.

What fails on a M20

failure defects by component group · advisories excluded

Component group	Defects	% of defects	vs all bikes
lighting and signalling	26	35.6	0.3×
brakes	17	23.3	0.3×
steering and suspension	14	19.2	0.3×
tyres and wheels	8	11	0.2×
fuel and exhaust	6	8.2	0.5×
body and structure	1	1.4	0.2×
driving controls	1	1.4	0.3×

Defects recorded against failed normal tests, 2005–2025, grouped by DVSA inspection section. One test can record multiple defects. "vs all bikes" is how often this model's tests record a defect in the group, as a multiple of the all-bike rate.

How rivals compare

same type, similar capacity, high test volume

On first-time pass rate the M20 beats 4 of its 4 closest rivals (KAWASAKI ZX-6R, SUZUKI GSF600, YAMAHA FZS600).

KAWASAKI ZX-6R 78.1% pass · 174k tests SUZUKI GSF600 77.3% pass · 143k tests YAMAHA FZS600 82.6% pass · 137k tests SUZUKI SV650S 80.6% pass · 84.6k tests

Rivals share this bike's type and sit within ±30% of its engine capacity, ≥ 5,000 tests. Card colour = better/worse first-time pass rate than the M20.

Pass rate by registration year

how each model-year cohort fares · registration year from first use date

Best year to buy used: 1940 (97.5% pass). Weakest: 1944 (80.6%).

First-time pass rate by the year each bike was first registered (cohorts with ≥ 50 tests). Older cohorts are survivors: the worst examples have already left the road, which tends to lift the earliest years.

BSA M20 FAQ

answers computed from the data above · terms in the glossary

Is the BSA M20 reliable?

The BSA M20 is more reliable than average for its class: 91.4% of its 1,295 MOT tests (2005–2025) passed first time, against a class average of 84.9%. That ranks it #587 of 5426 models.

What does a M20 fail its MOT on most?

lighting and signalling — 36% of all defects recorded against failed M20 tests.

What is the best year of M20 to buy used?

By first-time pass rate, 1947-registered examples do best (97.5%) and 1944 worst (80.6%). Condition and history still trump the year.

How many miles will a M20 last?

The median M20 shows 7,746 miles at test, and examples around 40k miles still pass 92.8% of the time — mileage alone rarely kills one.